Patent Publication Number: US-10333023-B2

Title: Method of manufacturing semiconductor light emitting device

Description:
RELATED APPLICATIONS 
     This application is a continuation of pending application Ser. No. 15/604,469, filed May 24, 2017, which in turn is a continuation of Ser. No. 14/612,244, filed Feb. 2, 2015, which in turn is a continuation of application Ser. No. 14/080,455, filed Nov. 14, 2013, now U.S. Pat. No. 8,975,653 B2, issued Mar. 10, 2015, which is a divisional of application Ser. No. 13/125,256 filed Jul. 11, 2011, now U.S. Pat. No. 8,686,454, issued Apr. 1, 2014, which is the U.S. National Phase under 35 U.S.C. § 371 of International Application No. PCT/KR2009/006144, filed on Oct. 22, 2009, which in turn claims the benefit of Korean Patent Applications No. 10-2008-0103671, filed Oct. 22, 2008, No. 10-2009-0100912, filed Oct. 22, 2009, the disclosures of which applications are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a semiconductor light emitting device, and more particularly, to a semiconductor light emitting device capable of performing an operation at a high current and improving luminous efficiency by changing an electrode arrangement structure. 
     BACKGROUND ART 
     Semiconductor light emitting devices include materials that emit light. For example, light emitting diodes (LEDs) are devices that use diodes, to which semiconductors are bonded, convert energy generated by the recombination of electrons and holes into light, and emit the light. The semiconductor light emitting devices are widely used in applications such as lighting, display devices and light sources, and the development thereof has been expedited. 
     In general, semiconductor junction light emitting devices have a junction structure of p-type and n-type semiconductors. In the semiconductor junction structure, light may be emitted by the recombination of electrons and holes at junction regions of both types of semiconductors, and further an active layer may be formed between both types of semiconductors in order to activate light emission. The semiconductor junction light emitting devices have a vertical structure and a horizontal structure according to the positions of electrodes for semiconductor layers. The horizontal structure includes an epi-up structure and a flip-chip structure. 
       FIG. 1  is a view illustrating a horizontal semiconductor light emitting device according to the related art and  FIG. 2  is a cross-sectional view illustrating a vertical semiconductor light emitting device according to the related art. For convenience of explanation, in  FIGS. 1 and 2 , a description will be made on the assumption that an n-type semiconductor layer is in contact with a substrate and a p-type semiconductor layer is formed on an active layer. 
     First, a horizontal semiconductor light emitting device will be described with reference to  FIG. 1 . 
     A horizontal semiconductor light emitting device  1  includes a non-conductive substrate  13 , an n-type semiconductor layer  12 , an active layer  11 , and a p-type semiconductor layer  10 . An n-type electrode  15  and a p-type electrode  14  are formed on the n-type semiconductor layer  12  and the p-type semiconductor layer  10 , respectively, and are electrically connected to an external current source (not shown) in order to apply voltage to the semiconductor light emitting device  1 . 
     When voltage is applied to the semiconductor light emitting device  1  through the electrodes  14  and  15 , electrons move from the n-type semiconductor layer  12  and holes move from the p-type semiconductor layer  10 , which results in the recombination of the electrons and the holes to emit light. The semiconductor light emitting device  1  includes the active layer  11  and the light is emitted from the active layer  11 . In the active layer  11 , the light emission of the semiconductor light emitting device  1  is activated and light is emitted. In order to make an electrical connection, the n-type electrode  15  and the p-type electrode  14  are positioned on the n-type semiconductor layer  12  and the p-type semiconductor layer  10 , respectively, with the lowest contact resistance values. 
     The positions of the electrodes may be varied according to substrate types. For instance, in the case that the substrate  13  is a sapphire substrate that is a non-conductive substrate as shown in  FIG. 1 , the electrode of the n-type semiconductor layer  12  cannot be formed on the non-conductive substrate  13 , but should be formed on the n-type semiconductor layer  12 . 
     Therefore, when the n-type electrode  15  is formed on the n-type semiconductor layer  12 , parts of the p-type semiconductor layer  10  and the active layer  11  that are formed at an upper side are consumed to form an ohmic contact portion. Since the electrodes are formed in this way, a light emitting area of the semiconductor light emitting device  1  is reduced, and thus luminous efficiency also decreases. 
     In order to solve a variety of problems including the above-described problems, a semiconductor light emitting device that uses a conductive substrate, rather than the non-conductive substrate, has appeared. 
     A semiconductor light emitting device  2 , as shown in  FIG. 2 , is a vertical semiconductor light emitting device. Since a conductive substrate  23  is used, an n-type electrode  25  may be formed on the substrate. Although, as shown in  FIG. 2 , the n-type electrode is formed on the conductive substrate  23 , a vertical light emitting device may also be manufactured by growing semiconductor layers by using a non-conductive substrate, removing the substrate, and then directly forming an n-type electrode on an n-type semiconductor layer. 
     When the conductive substrate  23  is used, since voltage can be applied to an n-type semiconductor layer  22  through the conductive substrate  23 , an electrode may be formed directly on the substrate. 
     Therefore, as shown in  FIG. 2 , the n-type electrode  25  is formed on the conductive substrate  23  and a p-type electrode  24  is formed on a p-type semiconductor layer  20 , thereby manufacturing a semiconductor light emitting device having a vertical structure. 
     However, in this case, particularly in the case that a high-power light emitting device having a large area is manufactured, an area ratio of the electrode to the substrate needs to be high for current spreading. As a result, light extraction is limited and light loss is caused due to optical absorption, and further luminous efficiency is reduced. 
     The horizontal and vertical semiconductor light emitting devices, which are described with reference to  FIGS. 1 and 2 , have a reduced light emitting area to reduce luminous efficiency, limit light extraction, and cause light loss due to the optical absorption. 
     For this reason, a semiconductor light emitting device having a new structure needs to be urgently developed in order to solve the problems of the conventional semiconductor light emitting devices. 
     DISCLOSURE 
     Technical Problem 
     An aspect of the present invention provides a semiconductor light emitting device having a new structure. 
     An aspect of the present invention also provides a semiconductor light emitting device with high luminous efficiency. 
     An aspect of the present invention also provides a high-current semiconductor light emitting device. 
     Technical Solution 
     According to an aspect of the present invention, there is provided a semiconductor light emitting device including a light emitting structure having a conductive substrate, a first electrode layer, an insulating layer, a second electrode layer, a second semiconductor layer, an active layer, and a first semiconductor layer sequentially stacked. Here, the second electrode layer includes at least one exposed region formed by exposing a portion of an interface in contact with the second semiconductor layer. The first electrode layer penetrates the second electrode layer, the second semiconductor layer, and the active layer and is electrically connected to the first semiconductor layer by being extended to predetermined regions of the first semiconductor layer through a plurality of contact holes penetrating the predetermined regions of the first semiconductor layer. The insulating layer insulates the first electrode layer from the second electrode layer, the second semiconductor layer and the active layer by being provided between the first electrode layer and the second electrode layer and on side surfaces of the contact holes. A contact area between the first electrode layer and the first semiconductor layer is 0.615% to 15.68% of a total area of the light emitting structure. 
     The contact holes may be uniformly arranged. 
     The number of the contact holes may be 1 to 48,000. 
     The contact area between the first electrode layer and the first semiconductor layer may be 6,150 μm 2  to 156,800 μm 2  per 1,000,000 μm 2  area of the semiconductor light emitting device. 
     A distance between central points of adjacent contact holes among the contact holes may be 5 μm to 500 μm. 
     The semiconductor light emitting device may further include an electrode pad portion formed on the exposed region of the second electrode layer. 
     The exposed region of the second electrode layer may be formed at a corner of the semiconductor light emitting device. 
     The second electrode layer may reflect light generated from the active layer. 
     The second electrode layer may include one selected from the group consisting of Ag, Al, Pt, Ni, Pt, Pd, Au, Ir and a transparent conductive oxide. 
     The conductive substrate may include one selected from the group consisting of Au, Ni, Al, Cu, W, Si, Se, and GaAs. 
     The contact area between the first electrode layer and the first semiconductor layer may be 3% to 13% of the total area of the light emitting structure. 
     According to another aspect of the present invention, there is provided a semiconductor light emitting device including a conductive substrate; a light emitting structure having a second semiconductor layer, an active layer, and a first semiconductor layer sequentially stacked; a first electrode layer including contact holes in contact with an inside of the first semiconductor layer by penetrating the second semiconductor layer and the active layer and an electrical connection portion extended from the contact holes and exposed outwardly of the light emitting structure; and an insulating layer electrically separating the first electrode layer from the conductive substrate, the second semiconductor layer and the active layer. Here, a contact area between the contact holes and the first semiconductor layer is 0.615% to 15.68% of a total area of the light emitting structure. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a horizontal semiconductor light emitting device according to the related art; 
         FIG. 2  is a cross-sectional view illustrating a vertical semiconductor light emitting device according to the related art; 
         FIG. 3  is a plan view illustrating a semiconductor light emitting device according to an exemplary embodiment of the present invention; 
         FIG. 4  is a cross-sectional view illustrating a semiconductor light emitting device according to an exemplary embodiment of the present invention; 
         FIG. 5  is a graph illustrating n-type ohmic contact resistance and p-type ohmic contact resistance of a semiconductor light emitting device having an area of 1,000×1,000 μm 2 ; 
         FIG. 6  is a graph illustrating the total resistance of a first contact resistance and a second contact resistance according to the contact area between a first semiconductor layer and a first electrode layer; 
         FIG. 7  is a graph illustrating luminous efficiency according to the contact area between the first semiconductor layer and the first electrode layer; 
         FIG. 8  is a view illustrating a modification of the semiconductor light emitting device of  FIG. 4 ; 
         FIG. 9  is a cross-sectional view illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 10 and 11  illustrate the result of a simulation conducted by changing n-type specific contact resistance; 
         FIGS. 12 through 16  are views illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 17 through 20  are views illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 21 through 25  are views illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 26 through 36  are views illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 37 through 57  are views illustrating semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 58 through 77  are views illustrating semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 78 through 91  are views illustrating semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 92 through 102  are views illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention; 
         FIGS. 103 through 105  are schematic views illustrating various embodiments of a white light emitting device package according to an exemplary embodiment of the present invention; 
         FIG. 106  illustrates the light emission spectrum of a white light emitting device package according to an exemplary embodiment of the present invention; 
         FIGS. 107A through 107D  illustrate the light emission characteristics of green phosphors applicable to the present invention; 
         FIG. 108A  and  FIG. 108B  illustrate light emission spectrums showing the light emission characteristics of green phosphors applicable to the preset invention; 
         FIGS. 109A and 109B  illustrate light emission spectrums showing the light emission characteristics of yellow phosphors applicable to the present invention; 
         FIGS. 110 and 111  are cross-sectional views illustrating white various embodiments of a white light source module according to another exemplary embodiment of the present invention; 
         FIGS. 112 and 113  are schematic views illustrating various embodiments of a light emitting device package according to another exemplary embodiment of the present invention; 
         FIGS. 114A through 114C  are schematic views illustrating the process of forming an external lead frame in the light emitting device package depicted in  FIG. 112 ; 
         FIGS. 115 through 117  are graphs showing the X-ray diffraction analysis result, light emission spectrum and excitation spectrum of β-sialon phosphors manufactured according to inventive example 1; 
         FIGS. 118A, 118B, and 119  are schematic perspective views illustrating a surface light source device having a flat light guide plate, and the light guide plate according to an exemplary embodiment of the present invention; and 
         FIGS. 120 through 125  are views illustrating a backlight unit having a flat light guide plate according to another exemplary embodiment of the present invention. 
     
    
    
     MODE FOR INVENTION 
     Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
     The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the shapes and dimensions may be exaggerated for clarity, and the same reference numerals will be used throughout to designate the same or like elements. 
     First, a semiconductor light emitting device will be described in detail through a variety of exemplary embodiments, and a light emitting device package and a backlight device using the same will also be described. 
     Semiconductor Light Emitting Device 
       FIGS. 3 and 4  are a plan view and a cross-sectional view illustrating a semiconductor light emitting device according to an exemplary embodiment of the present invention. Here,  FIG. 4  is a cross-sectional view taken along a line I-I′ shown in  FIG. 3 . 
     Referring to  FIGS. 3 and 4 , a semiconductor light emitting device  100  according to an exemplary embodiment of the invention includes a conductive substrate  110 , a first electrode layer  120 , an insulating layer  130 , a second electrode layer  140 , a second semiconductor layer  150 , an active layer  160 , and a first semiconductor layer  170  which are sequentially stacked. 
     The conductive substrate  110  may be formed of an electrically conductive material. The conductive substrate  110  may be formed of a material including any one of Au, Ni, Al, Cu, W, Si, Se, and GaAs, for example, an alloy of Si and Al. 
     The first electrode layer  120  is stacked on the conductive substrate  110 . Since the first electrode layer  120  is electrically connected to the conductive substrate  110  and the active layer  160 , the first electrode layer  120  may be formed of a material capable of minimizing contact resistance with the conductive substrate  110  and the active layer  160 . 
     The first electrode layer  120  is stacked on the conductive substrate  110  and further, some portions thereof, as shown in  FIG. 4 , penetrate the insulating layer  130 , the second electrode layer  140 , the second semiconductor layer  150  and the active layer  160  and are in contact with the first semiconductor layer  170  by being extended through contact holes  180  which penetrate predetermined regions of the first semiconductor layer  170 , whereby the conductive substrate  110  and the first semiconductor layer  170  are electrically connected. 
     That is, the first electrode layer  120  electrically connects the conductive substrate  110  to the first semiconductor layer  170  through the contact holes  180 . The conductive substrate  110  and the first semiconductor layer  170  are electrically connected through areas which are the size of the contact holes  180 , more exactly, contact regions  190  that are areas in which the first electrode layer  120  and the first semiconductor layer  170  are in contact with each other through the contact holes  180 . 
     Meanwhile, the insulating layer  130  is formed on the first electrode layer  120  in order to electrically insulate the first electrode layer  120  from other layers except for the conductive substrate  110  and the first semiconductor layer  170 . In other words, the insulating layer  130  may be formed not only between the first and second electrode layers  120  and  140 , but also between the first electrode layer  120  and the side surfaces of the second electrode layer  140 , the second semiconductor layer  150  and the active layer  160  which are exposed by the contact holes  180 . Furthermore, the insulating layer  130  may be formed on side surfaces of the predetermined regions of the first semiconductor layer  170  which the contact holes  180  penetrate to achieve insulation. 
     The second electrode layer  140  is formed on the insulating layer  130 . As described above, the second electrode layer  140  is not formed on the predetermined regions which the contact holes  180  penetrate. 
     Here, the second electrode layer  140 , as shown in  FIG. 4 , includes at least one region where a portion of an interface in contact with the second semiconductor layer  150  is exposed, i.e., an exposed region  145 . An electrode pad portion  147  may be formed on the exposed region  145  in order to connect an external current source to the second electrode layer  140 . Meanwhile, the second semiconductor layer  150 , the active layer  160 , and the first semiconductor layer  170 , which will be described later, are not formed on the exposed region  145 . Further, the exposed region  145 , as shown in  FIG. 3 , may be formed at the corners of the semiconductor light emitting device  100  in order to maximize a light emitting area of the semiconductor light emitting device  100 . 
     Meanwhile, the second electrode layer  140  may be formed of a material including any one of Ag, Al, Pt, Ni, Pt, Pd, Au, Ir and a transparent conductive oxide. This is because the second electrode layer  140  may be formed as a layer, a characteristic of which is the minimization of contact resistance with the second semiconductor layer  150 , since the second electrode layer  140  is in electrical contact with the second semiconductor layer  150 , and has a function of improving luminous efficiency by reflecting light generated from the active layer  160  outward. 
     The second semiconductor layer  150  is formed on the second electrode layer  140 . The active layer  160  is formed on the second semiconductor layer  150 . The first semiconductor layer  170  is formed on the active layer  160 . 
     Here, the first semiconductor layer  170  may be an n-type nitride semiconductor and the second semiconductor layer  150  may be a p-type nitride semiconductor. 
     Meanwhile, the active layer  160  may be formed by selecting different materials according to materials of which the first and second semiconductor layers  170  and  150  are formed. That is, since the active layer  160  is a layer in which energy generated by the recombination of electrons and holes is converted into light and the light is emitted, the active layer  160  may be formed of a material having a smaller energy band gap than those of the first semiconductor layer  170  and the second semiconductor layer  150 . 
       FIG. 8  illustrates a modification of the semiconductor light emitting device of  FIG. 4 . A semiconductor light emitting device  100 ′ of  FIG. 8  has the same structure as that of  FIG. 4 , except that it has passivation layers  191  formed on the side surfaces of a light emitting structure including the second semiconductor layer  150 , the active layer  160  and the first semiconductor layer  170 , and an unevenness formed on the top surface of the first semiconductor layer  170 . The passivation layer  191  protects the light emitting structure, particularly the active layer  160 , from the outside. The passivation layer  191  may be formed of a silicon oxide and a silicon nitride such as SiO 2 , SiO x N y  and Si x N y , and its thickness may be 0.1 μm to 2 μm. The active layer  160 , exposed outwardly, may function as a current leakage path during the operations of the semiconductor light emitting device  100 ′. Such a leakage may be prevented by forming the passivation layers  191  on the side surfaces of the light emitting structure. As shown in  FIG. 8 , when unevenness is formed on the passivation layers  191 , an improved light extraction effect may be expected. Likewise, the unevenness may be formed on the top surface of the first semiconductor layer  170 , and accordingly, light incident in a direction of the active layer  160  may be increasingly emitted outwards. Although not shown, when the light emitting structure is etched in order to expose the second electrode layer  140  in the manufacturing process, an etch stop layer may be further formed on the second electrode layer  140  in order to prevent the material forming the second electrode layer  140  from adhering to the side surface of the active layer  160 . The above-described modified embodiment of  FIG. 8  may be applicable to an exemplary embodiment of  FIG. 9 . 
     Meanwhile, the semiconductor light emitting device proposed in the present invention may have a structure modified in such a manner that the first electrode layer connected to the contact holes may be exposed outwardly.  FIG. 9  is a cross-sectional view illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention. A semiconductor light emitting device  200  according to this embodiment may have a second semiconductor layer  250 , an active layer  260  and a first semiconductor layer  270  formed on a conductive substrate  210 . In this case, a second electrode layer  240  may be disposed between the second semiconductor layer  250  and the conductive substrate  210 . Unlike the aforementioned embodiment, the second electrode layer  240  is not necessarily required. According to this embodiment, contact holes  280  having contact regions  290  in contact with the first semiconductor layer  270  are connected to a first electrode layer  220 . The first electrode layer  220  is exposed outwardly to have an electrical connection portion  245 . An electrode pad portion  247  may be formed on the electrical connection portion  245 . The first electrode layer  220  may be electrically separated from the active layer  260 , the second semiconductor layer  250 , the second electrode layer  240  and the conductive substrate  210  by an insulating layer  230 . Unlike the contact holes connected to the conductive substrate in the aforementioned embodiment, the contact holes  280  according to this embodiment are electrically separated from the conductive substrate  210 , and the first electrode layer  220  connected to the contact holes  280  is exposed outwardly. Accordingly, the conductive substrate  210  is electrically connected to the second semiconductor layer  240  and has a polarity different from that of the aforementioned embodiment. 
     Hereinafter, an optimal state of the contact holes in terms of size and shape will be found through a simulation regarding changes in electrical characteristics according to a contact area between the first electrode layer and the first semiconductor layer in the semiconductor light emitting device proposed in the present invention. In this case, the result of the simulation below may be applicable to the structures of  FIGS. 3 and 8 . Also, the first and second semiconductor layers are formed of n-type and p-type semiconductor layers, respectively. 
       FIG. 5  is a graph illustrating n-type ohmic contact resistance and p-type ohmic contact resistance of a semiconductor light emitting device having an area of 1,000×1,000 μm 2 . 
     In the simulation of  FIG. 5 , n-type specific contact resistance, namely, specific contact resistance of the first electrode layer  120  and the contact holes  180  is 10 −4  ohm/cm 2  while p-type specific contact resistance, namely, specific contact resistance of the second semiconductor layer  150  and the second electrode layer  140  is 10 −2  ohm/cm 2 . 
     Referring to  FIG. 5 , assuming that the semiconductor light emitting device  100  according to this embodiment of the invention is a rectangular chip having a size of 1,000,000 μm 2 , that is, a width which is 1,000 μm and a height which is 1,000 μm, the resistance of the semiconductor light emitting device  100  includes the first electrode layer  120 , the second electrode layer  140 , the first semiconductor layer  170 , and the second semiconductor layer  150 , contact resistance between the second semiconductor layer  150  and the second electrode layer  140  (hereinafter, referred to as “second contact resistance”), and contact resistance between the first semiconductor layer  170  and the first electrode layer  120  (hereinafter, referred to as “first contact resistance”), wherein major changes are made to the first contact resistance R 1  and the second contact resistance R 2  according to a contact area. 
     In particular, as shown in  FIG. 5 , as the contact area increases, more change is made to the first contact resistance R 1  as compared to the second contact resistance R 2 . Here, the X axis of  FIG. 5  represents the size of the contact area in which the first semiconductor layer  170  and the first electrode layer  120  are in contact with each other, and the Y axis of  FIG. 5  represents contact resistance values. Therefore, the figures of the X axis represent contact areas in which the first semiconductor layer  170  and the first electrode layer  120  are in contact with each other. As for the contact area between the second semiconductor layer  150  and the second electrode layer  140 , a value obtained by subtracting a value of the X axis from the total area (1,000,000 μm 2 ) of the semiconductor light emitting device  100  corresponds to the contact area between the second semiconductor layer  150  and the second electrode layer  140  which corresponds to the second contact resistance R 2 . 
     Here, the contact area between the first semiconductor layer  170  and the first electrode layer  120  indicates the total area of the contact regions  190  where the first electrode layer  120  and the first semiconductor layer  170  are in contact with each other through the contact holes  180  as described with reference to  FIGS. 3 and 4 , i.e., the sum total of areas of the contact regions  190  since there are a plurality of contact holes  180 . 
       FIG. 6  is a graph illustrating the total resistance of the first contact resistance and the second contact resistance according to the contact area between the first semiconductor layer and the first electrode layer. 
     Referring to  FIG. 6 , since the first contact resistance R 1  and the second contact resistance R 2  of the semiconductor light emitting device  100  according to this embodiment are connected to each other in series, the total resistance R 3  obtained by adding the first contact resistance R 1  and the second contact resistance R 2  among the resistances of the semiconductor light emitting device  100  is most deeply influenced by the contact area. 
     Here, as shown in  FIG. 6 , it is understood that as the contact area (referring to the values of the X axis) between the first semiconductor layer  170  and the first electrode layer  120  increases, the total resistance R 3  (referring to the values of Y axis) rapidly decreases at an early stage, and as the contact area between the first semiconductor layer  170  and the first electrode layer  120  further increases, the total resistance R 3  tends to increase. 
     Meanwhile, when the size of the semiconductor light emitting device  100  is 1,000,000 μm 2 , the n-type and p-type contact resistance of the semiconductor light emitting device  100  is preferably below 1.6 ohm so that the contact area between the first semiconductor layer  170  and the first electrode layer  120  is approximately 30,000 μm 2  to 250,000 μm 2 . 
     A semiconductor light emitting device usually operates at an operation voltage of 3.0 V to 3.2 V and at an operation current of approximately 0.35 A. If the total resistance of the semiconductor light emitting device is approximately 2 ohm, the voltage becomes 0.70 V according to the Equation of 0.35 A×2 ohm=0.70 V, which is beyond the common range of 2.8 V to 3.8 V. When the voltage is beyond the range, modifications of circuit configuration may be required, and also heat and light output degradation may occur due to an increase in input power. Therefore, the total resistance of the semiconductor light emitting device is preferably below 2 ohm, and since the sum of n-type and p-type contact resistance corresponds to approximately 80% of the total resistance, a reference contact resistance is 1.6 ohm derived from the Equation of 2 ohm×0.8=1.6 ohm. 
     That is, in the semiconductor light emitting device  100  as described with reference to  FIGS. 3 and 4 , it is most preferable in terms of contact resistance that the total contact area of the contact regions  190  where the first electrode layer  120  and the first semiconductor layer  170  are in contact with each other through the contact holes  180  be approximately 30,000 μm 2  to 250,000 μm 2 . 
       FIG. 7  is a graph illustrating luminous efficiency according to the contact area between the first semiconductor layer and the first electrode layer. 
     As described with reference to  FIG. 6 , when the contact area between the first semiconductor layer  170  and the first electrode layer  120  is 30,000 μm 2  to 250,000 μm 2 , the total resistance is low, and accordingly, the luminous efficiency of the semiconductor light emitting device  100  is likely to be high. However, it is not considered that as the contact area between the first semiconductor layer  170  and the first electrode layer  120  increases, a light emitting area of the semiconductor light emitting device  100  is practically reduced. 
     That is, as shown in  FIG. 7 , the luminous efficiency of the semiconductor light emitting device  100  increases by reducing the total resistance until the contact area between the first semiconductor layer  170  and the first electrode layer  120  is 70,000 μm 2 . However, when the contact area between the first semiconductor layer  170  and the first electrode layer  120  continuously increases above 70,000 μm 2 , luminous efficiency becomes lower. An increase in the contact area between the first semiconductor layer  170  and the first electrode layer  120  indicates a decrease in the contact area between the second semiconductor layer  150  and the second electrode layer  140 , which reduces a light-emitting amount of the semiconductor light emitting device  100 . 
     Therefore, the contact area between the first semiconductor layer  170  and the first electrode layer  120  needs to be appropriately determined, that is, the contact area between the first semiconductor layer  170  and the first electrode layer  120  is preferably below 130,000 μm 2  so that the level of luminous efficiency is above 90% as shown in  FIG. 7 . 
     As a result, in the semiconductor light emitting device  100  according to this embodiment, it is most preferable that the contact area between the first semiconductor layer  170  and the first electrode layer  120  through the contact holes  180  be 30,000 μm 2  to 130,000 μm 2 . Since the semiconductor light emitting device  100  corresponds to a case where the chip size is 1,000,000 μm 2 , a contact area between the first electrode layer  120  and the first semiconductor layer  170  that is 3% to 13% of the total area of the semiconductor light emitting device  100 , is the most proper amount of contact area. 
     Meanwhile, when the number of the contact holes  180  is very small, the contact area between the first semiconductor layer  170  and the first electrode layer  120  for each of the contact regions  190  between the first semiconductor layer  170  and the first electrode layer  120  increases, and accordingly, the area of the first semiconductor layer  170  to which current needs to be supplied increases, and the amount of current which should be supplied to the contact regions  190  also increases. This causes a current-crowding effect at the contact regions  190  between the first semiconductor layer  170  and the first electrode layer  120 . 
     In addition, when the number of the contact holes  180  is very large, the size of each of the contact holes  180  necessarily becomes very small, thereby causing difficulty in the manufacturing process. 
     The number of the contact holes  180  may therefore be properly selected according to the size of the semiconductor light emitting device  100 , i.e., the chip size. When the size of the semiconductor light emitting device  100  is 1,000,000 μm 2 , the number of the contact holes  180  may be 5 to 50. 
     Meanwhile, when the plurality of contact holes  180  of the semiconductor light emitting device  100  are formed, the contact holes  180  may be uniformly arranged. In order to uniformly spread current, since the first semiconductor layer  170  and the first electrode layer  120  are in contact with each other through the contact holes  180 , the contact holes  180 , i.e., the contact regions  190  between the first semiconductor layer  170  and the first electrode layer  120  may be uniformly arranged. 
     Here, when the size of the semiconductor light emitting device  100  is 1,000,000 μm 2  and the number of the contact holes  180  is 5 to 50, separation distances between adjacent contact holes among the plurality of contact holes may be 100 μm to 400 μm, in order to uniformly arrange the semiconductor light emitting device  100 . The separation distances are values measured by connecting central points of the adjacent contact holes. 
     Meanwhile, the semiconductor light emitting device  100  is capable of achieving uniform current spreading by uniformly arranging the plurality of contact holes  180 . Contrary to a semiconductor light emitting device having a size of 1,000,000 μm 2 , which conventionally operates at approximately 350 mA, the semiconductor light emitting device  100  according to this embodiment of the invention operates stably and decreases the current crowding effect even though a high current of approximately 2 A is applied, resulting in the semiconductor light emitting device with improved reliability. 
       FIGS. 10 and 11  illustrate the result of a simulation conducted by changing n-type specific contact resistance. In this simulation, the n-type specific contact resistance is 10 −6  ohm/cm 2  and p-type specific contact resistance is 10 −2  ohm/cm 2 . The n-type specific contact resistance is influenced by the doping levels of the n-type semiconductor layer, n-type electrode materials, and heat treatment methods. Therefore, the n-type specific contact resistance may be reduced by up to 10 −6  ohm/cm 2  by increasing the doping concentration of the n-type semiconductor layer or adopting metal having a low energy barrier such as Al, Ti and Cr as an n-type electrode material. That is, the n-type specific contact resistance may be commonly 10 −4  ohm/cm 2  to 10 −6  ohm/cm 2 . 
     Referring to  FIG. 10 , the sum total of the n-type and p-type specific contact resistance, namely, the total contact resistance R 4  may be maintained at a very low level even in a smaller contact area, as compared with the result shown in  FIG. 6 . Also, as a result of reviewing luminous efficiency according to the contact area with reference to  FIG. 11 , luminous efficiency may be maintained at a high level even in a smaller contact area, as compared with the result shown in  FIG. 7 . In this case, the value of luminous efficiency above 100% indicates a value relative to the result shown in  FIG. 7 . Referring to the result of the simulation shown in  FIGS. 10 and 11 , the condition that the total contact resistance is below 1.6 ohm and the luminous efficiency is above 90% is when the contact area between the first electrode layer and the first semiconductor layer is 6150 μm 2  to 156,800 μm 2  per 1,000,000 μm 2  area. 
     When the number of contact holes is determined on the basis of such a result, the contents described with reference to the result of the previous simulation may be applied. Specifically, in the case of circular contact holes having a radius of approximately 1 μm to 50 μm, approximately 1 to 48,000 contact holes are required to satisfy the above condition. Further, assuming that the contact holes are uniformly arranged, the distance between two adjacent contact holes should be approximately 5 μm to 500 μm. 
     Hereinafter, a semiconductor light emitting device according to another exemplary embodiment of the present invention will be described through a variety of embodiments. 
     First, a semiconductor light emitting device according to another exemplary embodiment of the invention will be described with reference to  FIGS. 12 through 16 . 
     A semiconductor light emitting device  300  according to another exemplary embodiment of the invention includes a conductive substrate  340 , a first conductivity type semiconductor layer  330 , an active layer  320  and a second conductivity type semiconductor layer  310  that are sequentially stacked. This semiconductor light emitting device  300  includes a first electrode layer  360  formed between the conductive substrate  340  and the first conductivity type semiconductor layer  330 , and a second electrode part  350  including an electrode pad portion  350 - b , an electrode extension portion  350 - a , and an electrode connection portion  350 - c.    
     The electrode pad portion  350 - b  extends from the first electrode layer  360  to the surface of the second conductivity type semiconductor layer  310  and is electrically separated from the first electrode layer  360 , the first conductivity type semiconductor layer  330 , and the active layer  320 . The electrode extension portion  350 - a  extends from the first electrode layer  360  to the inside of the second conductivity type semiconductor layer  310  and is electrically separated from the first electrode layer  360 , the first conductivity type semiconductor layer  330 , and the active layer  320 . The electrode connection portion  350 - c  is formed in the same layer as the first electrode layer  360 , but is electrically separated from the first electrode layer  360 . The electrode connection portion  350 - c  connects the electrode pad portion  350 - b  to the electrode extension portion  350 - a.    
     The conductive substrate  340  may be a metallic substrate or a semiconductor substrate. When the conductive substrate  340  is the metallic substrate, the conductive substrate  340  may be formed of any one of Au, Ni, Cu, and W. Also, when the conductive substrate  340  is the semiconductor substrate, the conductive substrate  340  may be formed of any one of Si, Ge, and GaAs. Examples of a method of forming a conductive substrate in a semiconductor light emitting device include a plating method of forming a plating seed layer to form a substrate and a substrate bonding method of separately preparing a conductive substrate and bonding the conductive substrate by using a conductive adhesive, such as Au, Au—Sn, and Pb—Sr. 
     Each of the semiconductor layers  330  and  310  may be formed of an inorganic semiconductor such as a GaN-based semiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, a GaP-based semiconductor, and a GaAsP-based semiconductor. The semiconductor layers may be formed by using, for example, molecular beam epitaxy (MBE). In addition, the semiconductor layers may be formed of any one of semiconductors, such as a group III-V semiconductor, a group II-VI semiconductor and Si. 
     The active layer  320  is a layer where light emission is activated. The active layer  320  may be formed of a material having a smaller energy band gap than each of the first and second conductivity type semiconductor layers  330  and  310 . For example, when the first and second conductivity type semiconductor layers  330  and  310  may be a GaN-based compound semiconductor, the active layer  320  may be formed by using an InAlGaN-based compound semiconductor that has a smaller energy bandgap than GaN. That is, the active layer  320  may be In x Al y Ga (1-x-y) N (where 0≤x≤1, 0≤y≤1, and 0≤x+y≤1 are satisfied). 
     Here, in consideration of the characteristics of the active layer  320 , the active layer  320  is preferably not doped with impurities. A wavelength of emitted light may be controlled by adjusting a mole ratio of constituents. Therefore, the semiconductor light emitting device  300  may emit any one of infrared light, visible light, and UV light according to the characteristics of the active layer  320 . 
     An energy well structure appears in the entire energy band diagram of the semiconductor light emitting device  300  according to the active layer  320 . Electrons and holes from each of the semiconductor layers  330  and  310  are moving and are trapped within the energy well structure, which results in higher luminous efficiency. 
     The first electrode layer  360  electrically connects the first conductivity type semiconductor layer  330  to an external current source (not shown). The first electrode layer  360  may be formed of metal. For example, the first electrode layer  360  may be formed of Ti as an n-type electrode, and Pd or Au as a p-type electrode. 
     The first electrode layer  360  may reflect light generated from the active layer  320 . The reflected light is directed to a light emitting surface, and accordingly, the luminous efficiency of the semiconductor light emitting device  300  is improved. In order to reflect the light generated from the active layer  320 , the first electrode layer  360  may be formed of metal that appears white in a visible light region. For example, the white metal may be any one of Ag, Al, and Pt. The first electrode layer  360  will be further described with reference to  FIGS. 14A through 14C . 
     The second electrode part  350  electrically connects the second conductivity type semiconductor layer  310  to an external current source (not shown). The second electrode part  350  may be formed of metal. For example, the second electrode part  350  may be formed of Ti as an n-type electrode, and Pd or Au as a p-type electrode. Particularly, the second electrode part  350  according to this embodiment includes the electrode pad portion  350 - b , the electrode extension portion  350 - a , and the electrode connection portion  350 - c.    
     Referring to  FIG. 13A , the electrode pad portion  350 - b  is formed on the surface of the second conductivity type semiconductor layer  310 , and the plurality of electrode extension portions  350 - a , indicated by a dotted line, are located inside the second conductivity type semiconductor layer  310 . 
     In  FIG. 13B , the top surface of the second conductivity type semiconductor layer  310  shown in  FIG. 13A  is taken along lines A-A′, B-B′, and C-C′. The line A-A′ is taken to show a section that only includes the electrode extension portion  350 - a . The line B-B′ is taken to show a section that includes the electrode pad portion  350 - b  and the electrode extension portion  350 - a . The line C-C′ is taken to show a section that includes neither the electrode extension portion  350 - a  nor the electrode pad portion  350 - b.    
       FIGS. 14A through 14C  are cross-sectional views of the semiconductor light emitting device shown in  FIG. 13B  taken along lines A-A′, B-B′, and C-C′. Hereinafter, a detailed description will be made with reference to  FIGS. 12, 13A, 13B, and 14A through 14C . 
     In  FIG. 14A , the electrode extension portion  350 - a  extends from the first electrode layer  360  to the inside of the second conductivity type semiconductor layer  310 . The electrode extension portion  350 - a  passes through the first conductivity type semiconductor layer  330  and the active layer  320  and extends to the second conductivity type semiconductor layer  310 . The electrode extension portion  350 - a  extends at least to part of the second conductivity type semiconductor layer  310 . However, the electrode extension portion  350 - a  does not necessarily extend to the surface of the second conductivity type semiconductor layer  310 . This is because the electrode extension portion  350 - a  is used to spread current in the second conductivity type semiconductor layer  310 . 
     The electrode extension portion  350 - a  needs to have a predetermined area to spread the current in the second conductivity type semiconductor layer  310 . Contrary to the electrode pad portion  350 - b , the electrode extension portion  350 - a  is not used for the electrical connection. Therefore, the electrode extension portion  350 - a  is formed by a predetermined number so that each electrode extension portion  350 - a  has an area small enough to allow uniform current spreading in the second conductivity type semiconductor layer  310 . A small number of electrode extension portions  350 - a  may cause deterioration in electrical characteristics due to non-uniform current spreading. A large number of electrode extension portions  350 - a  may cause difficulty in the process of forming the electrode extension portions  350 - a  and a decrease in a light emitting area due to a decrease in the area of the active layer. Therefore, the number of electrode extension portions  350 - a  may be appropriately determined in consideration of these facts. Each of the electrode extension portions  350 - a  is formed to have as small an area as possible and allows for uniform current spreading. 
     The plurality of electrode extension portions  350 - a  may be formed for current spreading. Also, the electrode extension portion  350 - a  may have a cylindrical shape. A cross section of the electrode extension portion  350 - a  may be smaller than that of the electrode pad portion  350 - b . Further, the electrode extension portions  350 - a  may be separated from the electrode pad portion  350 - b  by a predetermined distance. The electrode extension portions  350 - a  and the electrode pad portion  350 - b  may be connected to each other in the first electrode layer  360  by the electrode connection portion  350 - c  to be described below. For this reason, the electrode extension portions  350 - a  are separated from the electrode pad portion  350 - b  by the predetermined distance, and thus induce uniform current spreading. 
     The electrode extension portions  350 - a  are formed from the first electrode layer  360  to the inside of the second conductivity type semiconductor layer  310 . Since the electrode extension portions  350 - a  are used for current spreading in the second conductivity type semiconductor layer  310 , the electrode extension portions  350 - a  need to be electrically separated from the other layers. Accordingly, the electrode extension portions  350 - a  are electrically separated from the first electrode layer  360 , the first conductivity type semiconductor layer  330 , and the active layer  320 . Electrical separation may be achieved by using an insulating material such as a dielectric. 
     In  FIG. 14B , the electrode pad portion  350 - b  extends from the first electrode layer  360  to the surface of the second conductivity type semiconductor layer  310 . The electrode pad portion  350 - b  starts from the first electrode layer  360 , passes through the first conductivity type semiconductor layer  330 , the active layer  320  and the second conductivity type semiconductor layer  310 , and extends to the surface of the second conductivity type semiconductor layer  310 . Since the electrode pad portion  350 - b  is formed to connect the second electrode part  350  to the external current source, at least one electrode pad portion  350 - b  needs to be included. 
     The electrode pad portion  350 - b  extends from the first electrode layer  360  to the surface of the second conductivity type semiconductor layer  310 . Since the electrode pad portion  350 - b  is electrically connected to the external current source at the surface of the second conductivity type semiconductor layer  310  to supply current to the electrode extension portions  350 - a , the electrode pad portion  350 - b  may be electrically separated from the first electrode layer  360 , the first conductivity type semiconductor layer  330 , and the active layer  320 . Electrical separation may be achieved by using an insulating material such as a dielectric. 
     The electrode pad portion  350 - b  supplies the current to the electrode extension portions  350 - a . Further, the electrode pad portion  350 - b  may be formed so that the electrode pad portion  350 - b  is not electrically separated from the second conductivity type semiconductor layer  310  so as to directly spread the current. The electrode pad portion  350 - b  may be electrically separated from the second conductivity type semiconductor layer  310  or not, according to whether current supply to the electrode extension portions  350 - a  or current spreading in the second conductivity type semiconductor layer  310  is required. 
     A cross section of the electrode pad portion  350 - b  at the active layer  320  may be smaller than that of the electrode pad portion  350 - b  at the surface of second conductivity type semiconductor layer  310 . In this way, the area of the active layer  320  is maximized as much as possible in order to ensure an increase in luminous efficiency. However, the electrode pad portion  350 - b  at the surface of the second conductivity type semiconductor layer  310  needs to have a predetermined area so as to be connected with the external current source. 
     The electrode pad portion  350 - b  may be located at the center of the semiconductor light emitting device  300 . In this case, the electrode extension portions  350 - a  are preferably separated from the electrode pad portion  350 - b  by the predetermined distance, and uniformly distributed. Referring to  FIG. 13A , the electrode pad portion  350 - b  and the electrode extension portions  350 - a  are uniformly distributed over the second conductivity type semiconductor layer  310  to optimize the current spreading. In  FIG. 13A , it is assumed that there are one electrode pad portion  350 - b  and twelve electrode extension portions  350 - a . However, the number of electrode pad portion  350 - b  and the number of electrode extension portions  350 - a  may be appropriately determined in considerations of factors for electrical connection state (e.g. the position of the external current source) and current spreading state (e.g. the thickness of the second conductivity type semiconductor layer  310 ). 
     When the plurality of electrode extension portions  350 - a  are formed, the electrode pad portion  350 - b  may be directly connected to each of the plurality of electrode extension portions  350 - a . In this case, the electrode pad portion  350 - b  is formed at the center of the semiconductor light emitting device  300 , and the electrode extension portions  350 - a  are formed around the electrode pad portion  350 - b . Further, the electrode connection portion  350 - c  may directly connect the electrode pad portion  350 - b  and the electrode extension portions  350 - a  in a radial direction. 
     Alternatively, some of the plurality of electrode extension portions  350 - a  may be directly connected to the electrode pad portion  350 - b . Other electrode extension portions  350 - a  may be connected to the electrode extension portions  350 - a  that are directly connected to the electrode pad portion  350 - b , such that these electrode extension portions  350 - a  are indirectly connected to the electrode pad portion  350 - b . In this way, a larger number of electrode extension portions  350 - a  can be formed to thereby increase current spreading efficiency. 
     In  FIGS. 14A through 14C , the electrode connection portion  350 - c  is formed in the first electrode layer  360  and connects the electrode pad portion  350 - b  and the electrode extension portions  350 - a  to each other. Therefore, a considerable amount of the second electrode part  350  is located at a rear surface opposite to the direction in which light is emitted from the active layer  320 , thereby increasing luminous efficiency. Particularly, in  FIG. 14C , only the electrode connection portion  350 - c  is located in the first electrode layer  360 . The second electrode part  350  is not located at the first conductivity type semiconductor layer  330 , the active layer  320 , and the second conductivity type semiconductor layer  310 . Accordingly, as shown in  FIG. 14C , the electrode pad portion  350 - b  and the electrode connection portions  350 - a  do not affect light emissions, so they have higher luminous efficiency. Although not shown in  FIG. 14C , the first electrode layer  360  may be in contact with the conductive substrate  340  to thereby be connected to the external current source. 
     The electrode connection portion  350 - c  is electrically separated from the first electrode layer  360 . The first electrode layer  360  and the second electrode part  350  include electrodes that have polarities opposite to each other to supply external power to the first conductivity type semiconductor layer  330  and the second conductivity type semiconductor layer  310 , respectively. Therefore, the two electrodes must be electrically separated from each other. Electrical separation may be achieved by using an insulating material, such as a dielectric. 
     In  FIG. 14B , since the electrode pad portion  350 - b  is located on the surface of the second conductivity type semiconductor layer  310 , it is possible to obtain characteristics of a vertical semiconductor light emitting device. In  FIG. 14C , since the electrode connection portion  350 - c  is located in the same plane as the first electrode layer  360 , it is possible to obtain the characteristics of a horizontal semiconductor light emitting device. Therefore, the semiconductor light emitting device  300  has a structure in which the horizontal semiconductor light emitting device and the vertical semiconductor light emitting device are integrated. 
     Referring to  FIGS. 14A through 14C , the second conductivity type semiconductor layer  310  may be an n-type semiconductor layer, and the second electrode part  350  may be an n-type electrode part. In this case, the first conductivity type semiconductor layer  330  may be a p-type semiconductor layer, and the first electrode layer  360  may be a p-type electrode. The second electrode part  350  includes the electrode pad portion  350 - b , the electrode extension portions  350 - a , and the electrode connection portion  350 - c  that are connected to each other. When the second electrode part  350  is formed of the n-type electrode, the second electrode part  350  may be electrically separated from the first electrode layer  360  formed of the p-type electrode by an insulating part  370  that is formed of an insulating material. 
       FIG. 15A  illustrates the light emission of a semiconductor light emitting device having an uneven pattern formed on the surface thereof according to a modified embodiment of this embodiment.  FIG. 15B  illustrates the current spreading of a semiconductor light emitting device having an uneven pattern formed on the surface thereof according to another modified embodiment of this embodiment. 
     The semiconductor light emitting device  300  according to this embodiment includes the second conductivity type semiconductor layer  310  that forms an outermost surface in a direction in which emitted light moves. Accordingly, it is easy to form an uneven pattern on the surface by using a method well-known in the art, such as photolithography. In this case, light emitted from the active layer  320  passes through an uneven pattern  380  that is formed on the surface of the second conductivity type semiconductor layer  310 , and then the light is extracted. The uneven pattern  380  increases light extraction efficiency. 
     The uneven pattern  380  may have a photonic crystal structure. Photonic crystals contain different media with different refractivity in which the media are regularly arranged in a crystal-like manner. The photonic crystals may increase light extraction efficiency by controlling light in unit of length corresponding to a multiple of a wavelength of light. The photonic crystal structure may be formed according to an appropriate process after forming the second conductivity type semiconductor layer  310  and the second electrode part  350 . For example, the photonic crystal structure may be formed through an etching process. 
     Even though the uneven pattern  380  is formed on the second conductivity type semiconductor layer  310 , current spreading is not affected by the uneven pattern  380 . Referring to  FIG. 15B , the current spreading in the electrode extension portions  350 - a  is not affected by the uneven pattern  380 . Each of the electrode extension portions  350 - a  spreads current below the uneven pattern  380  and the uneven pattern  380  extracts emitted light, thereby increasing luminous efficiency. 
       FIG. 16  is a graph illustrating the relationship between the current density and luminous efficiency of a light emitting surface. When current density is above approximately 10 A/cm 2  in the graph, a smaller level of current density indicates higher luminous efficiency and a larger level of current density indicates lower luminous efficiency. 
     Table 1 below shows values related thereto. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Light  
                 Current  
                 Luminous 
                 Improvement  
               
               
                   
                 Emitting 
                 Density 
                 Efficiency 
                 Rate 
               
               
                   
                 Area (cm 2 ) 
                 (A/cm 2 ) 
                 (lm/W) 
                 (%) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 0.0056 
                 62.5 
                 46.9 
                 100 
               
               
                   
                 0.0070 
                 50.0 
                 51.5 
                 110 
               
               
                   
                 0.0075 
                 46.7 
                 52.9 
                 113 
               
               
                   
                 0.0080 
                 43.8 
                 54.1 
                 115 
               
               
                   
                   
               
            
           
         
       
     
     As the light emitting area increases, luminous efficiency improves. However, in order to ensure the light emitting area, it is necessary to decrease the area of distributed electrodes, and accordingly, the current density of the light emitting surface tends to decrease. Such a decrease in the current density of the light emitting surface may deteriorate the electrical characteristics of the semiconductor light emitting device. 
     This problem may be solved by ensuring current spreading by using the electrode extension portions. That is, the problem of the electrical characteristics that may caused by the decrease in the current density may be addressed by forming the electrode extension portions in such a manner that the electrode extension portions are formed inside the light emitting device without extending to the light emitting surface and serve to spread current therein. Therefore, the semiconductor light emitting device according to this embodiment is capable of achieving desired current spreading and obtaining a maximum light emitting area, thereby improving luminous efficiency. 
     A semiconductor light emitting device according to another exemplary embodiment of the present invention will be described with reference to  FIGS. 17 through 20 . 
       FIG. 17  is a perspective view illustrating a light emitting device according to another exemplary embodiment of the present invention.  FIGS. 18A and 18B  are top views illustrating the light emitting device of  FIG. 17 .  FIGS. 19A through 19C  are cross-sectional views illustrating the light emitting device of  FIG. 18B , taken along lines A-A′, B-B′, and C-C′, respectively. 
     A light emitting device  400  according to another exemplary embodiment of the invention includes a light emitting stack  430 ,  420  and  410 , at least one barrier portion  470 , a second electrode structure  460 , a first electrode structure  440 , and a conductive substrate  450 . The light emitting stack  430 ,  420  and  410  includes first and second conductivity type semiconductor layers  430  and  410 , and an active layer  420  formed therebetween, and has a first surface and a second surface opposite to each other and provided as the first and second conductivity type semiconductor layers  430  and  410 . The barrier portion  470  has electrical insulation and extends from the second surface of the light emitting stack  430 ,  420  and  410  to at least part of the second conductivity type semiconductor layer  410  to divide the light emitting stack  430 ,  420  and  410  into a plurality of light emitting regions. The second electrode structure  460  is connected to the second conductivity type semiconductor layer  410  that is located at the plurality of light emitting regions. The first electrode structure  440  is formed on the second surface of the light emitting stack  430 ,  420  and  410  so as to be connected to the first conductivity type semiconductor layer  430 . The conductive substrate  450  is formed on the second surface of the light emitting stack  430 ,  420  and  410  so as to be electrically connected to the first electrode structure  440 . 
     The light emitting stack  430 ,  420  and  410  includes the first and second conductivity type semiconductor layers  430  and  410 , and the active layer  420  formed therebetween. The light emitting stack  430 ,  420  and  410  has an outer surface of the second conductivity type semiconductor layer  410  that serves as the first surface and an outer surface of the first conductivity type semiconductor layer  430  that serves as the second surface. 
     Each of the semiconductor layers  430  and  410  may be formed of a semiconductor, such as a GaN-based semiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, a GaP-based semiconductor, and a GaAsP-based semiconductor. The semiconductor layer may be formed by using, for example, molecular beam epitaxy (MBE). In addition, each of the semiconductor layers may be formed of any one of semiconductors, such as a group III-V semiconductor, a group II-VI semiconductor, and Si. The light emitting stack may grow on a non-conductive substrate (not shown), such as a sapphire substrate, having relatively small lattice-mismatching. The non-conductive substrate is removed later before a conductive substrate is bonded. 
     The active layer  420  is a layer in which light emission is activated. The active layer  420  is formed of a material that has a smaller energy bandgap than each of the second and first conductivity type semiconductor layers  410  and  430 . For example, when each of the second and first conductivity type semiconductor layers  410  and  430  is formed of a GaN-based compound semiconductor, the active layer  420  may be formed by using an InAlGaN-based compound semiconductor that has a smaller energy bandgap than GaN. That is, the active layer  420  may include In x Al y Ga (1-x-y) N (where 0≤x≤1, 0≤y≤1, and 0≤x+y≤1 are satisfied). 
     Here, in consideration of the characteristics of the active layer  420 , the active layer  420  is preferably not doped with impurities. A wavelength of emitted light may be controlled by adjusting a mole ratio of constituents. Therefore, the light emitting device  400  may emit any one of infrared light, visible light, and UV light according to the characteristics of the active layer  420 . 
     An energy well structure appears in the entire energy band diagram of the light emitting device  400  according to the active layer  420 . Electrons and holes from each of the semiconductor layers  430  and  410  are moving and are trapped within the energy well structure, which results in higher luminous efficiency. 
     The barrier portion  470  extends from the second surface of the light emitting stack  430 ,  420 , and  410  to at least part of the second conductivity type semiconductor layer  410 , such that the light emitting stack  430 ,  420 , and  410  is divided into the plurality of light emitting regions. The barrier portion  470  divides the second conductivity type semiconductor layer  410  into a plurality of regions. When a separating unit, such as a laser, is used between the second conductivity type semiconductor layer  410  and a substrate for growth (not shown) formed on the second conductivity type semiconductor layer  410 , the barrier portion  470  reduces stress that is generated due to heat energy applied to the interface therebetween. 
     For example, when a laser is used as the separating unit for separating the second conductivity type semiconductor layer  410  from the substrate for growth, the temperature at the interface is approximately 1000° C. Heat energy from the laser separates the second conductivity type semiconductor layer  410  from the substrate for growth. However, the heat generates stress that induces contraction and expansion of the semiconductor layers and the conductive substrate  450  to be bonded later. In general, since the magnitude of stress is in proportion to the area, the stress may adversely affect a large area light limiting device. 
     However, since the light emitting device  400  according to this embodiment includes the barrier portion  470 , the area of the second conductivity type semiconductor layer  410  is divided into a plurality of smaller areas of the plurality of light emitting regions to thereby reduce stress. That is, expansion and contraction are more easily performed according to the plurality of light emitting regions, such that light emission of the light emitting stack  430 ,  420 , and  410  can be stabilized. 
     Preferably, the barrier portion  470  electrically insulates the semiconductor layers  43 U and  410 , and the active layer  420 . To do so, the barrier portion  470  may be filled with air. Alternatively, the barrier portion  470  may have an insulating layer formed therein, in which the insulating layer is filled with air. Further, the entire barrier portion may be filled with an insulating material, such as a dielectric, to achieve electrical insulation. 
     In order to electrically insulate the light emitting stack  430  and  410 , the barrier portion  470  may extend from the second surface to the top surface of the second conductivity type semiconductor layer  410 . However, the barrier portion  470  does not necessarily extend to the top surface of the second conductivity type semiconductor layer  410 . The barrier portion  470  may extend to the inside of the second conductivity type semiconductor layer  410 . 
     Also, the barrier portion  470  may have a single structure. Alternatively, the barrier portion  470  may include a plurality of barriers that are separated from each other. In this case, the plurality of barriers may appear different from each other in order to allow required electrical insulating characteristics. For example, the barrier that surrounds a bonding portion  461  and the barrier that surrounds a contact hole  462  may be different in height and shape. 
     The second electrode structure  460  is connected to the second conductivity type semiconductor layer  410  located at the plurality of light emitting regions that are separated from each other by the barrier portion  470 . The second electrode structure  460  includes the contact hole  462 , the bonding portion  461 , and a wiring portion  463 . 
     There may be a plurality of contact holes  462 . Each of the plurality of contact holes  462  may be formed in each of the plurality of light emitting regions. A single contact hole may be formed in a single light emitting region or a plurality of contact holes may be formed in a single light emitting region. While the contact holes  462  are electrically connected to the second conductivity type semiconductor layer  410 , the contact holes  462  are electrically insulated from the first conductivity type semiconductor layer  430  and the active layer  420 . To do so, the contact hole  462  extends from the second surface of the light emitting stack  430 ,  420 , and  410  to at least part of the second conductivity type semiconductor layer  410 . The contact holes  462  are formed to spread current in the second conductivity type semiconductor layer  410 . 
     The bonding portion  461  is connected from the first surface of the light emitting stack  430 ,  420 , and  410  to at least one of the plurality of contact holes  462 . A region that is exposed at the first surface is provided as a bonding region. 
     The wiring portion  463  is formed at the second surface of the light emitting stack  430 ,  420 , and  410 . While the wiring portion  463  is electrically insulated from at least the first conductivity type semiconductor layer  430 , the wiring portion  463  electrically connects one contact hole  462 , which is connected to the bonding portion  461 , and another contact hole  462 . Also, the wiring portion  463  may connect the contact holes  462  to the bonding portion  461 . The wiring portion  463  is located below the second conductivity type semiconductor layer  410  and the active layer  420  to thereby increase luminous efficiency. 
     Hereinafter, the contact holes  462 , the bonding portion  461 , and the wiring portion  463  will be described in more detail with reference to  FIGS. 18A through 19C . 
     The first electrode structure  440  is formed on the second surface of the light emitting stack  430 ,  420 , and  410  so as to be electrically connected to the first conductivity type semiconductor layer  430 . That is, the first electrode structure  440  has an electrode that electrically connects the first conductivity type semiconductor layer  430  to an external current source (not shown). The first electrode structure  440  may be formed of metal. For example, the first electrode structure  440  may be formed of Ti as an n-type electrode, and Pd or Au as a p-type electrode. 
     The first electrode structure  440  may reflect light generated from the active layer  420 . Since the first electrode structure  440  is located below the active layer  420 , the first electrode structure  440  is located at a surface opposite to a direction, in which the light emitting device emits light, on the basis of the active layer  420 . Light moving from the active layer  420  to the first electrode structure  440  is opposite to the light emitting direction, and thus the light needs to be reflected to increase luminous efficiency. Therefore, the light reflected by the first electrode structure  440  moves toward a light emitting surface, thereby increasing the luminous efficiency of the light emitting device. 
     In order to reflect the light generated from the active layer  420 , the first electrode structure  440  may be formed of metal that appears white in the visible light region. For example, the white metal may be any one of Ag, Al, and Pt. The first electrode structure  440  will be described below in more detail with reference to  FIGS. 19A through 19C . 
     The conductive substrate  450  is formed on the second surface of the light emitting stack  430 ,  420 , and  410  so as to be electrically connected to the first electrode structure  440 . The conductive substrate  450  may be a metallic substrate or a semiconductor substrate. When the conductive substrate  450  is the metallic substrate, the conductive substrate  450  may be formed of any one of Au, Ni, Cu, and W. Further, when the conductive substrate  450  is the semiconductor substrate, the conductive substrate  450  may be formed of any one of Si, Ge, and GaAs. Examples of a method of forming a conductive substrate in a light emitting device include a plating method of forming a plating seed layer to form a substrate and a substrate bonding method of separately preparing a conductive substrate and bonding the conductive substrate by using a conductive adhesive, such as Au, Au—Sn, and Pb—Sr. 
     Referring to  FIG. 18A , the bonding portion  461  is formed on the surface of the second conductivity type semiconductor layer  410 , and the plurality of contact holes  462 , indicated by a dotted line, are located inside the second conductivity type semiconductor layer  410 . The second conductivity type semiconductor layer  410  includes the plurality of light emitting regions that are separated from each other by the barrier portion  470 . In  FIGS. 18A and 18B , only one bonding portion  461  is shown. However, a plurality of bonding portions may be formed on the same light emitting region or a plurality of bonding portions may be formed on each of the plurality of light emitting regions. Further, each of the contact holes  462  is formed in each of the light emitting regions. However, the plurality of contact holes  462  may be formed in a single light emitting region to thereby improve current spreading. 
     In  FIG. 18B , the top surface of the second conductivity type semiconductor layer  410  shown in  FIG. 18A  is taken along lines A-A′, B-B′, and C-C′. The line A-A′ is taken to show a section that only includes the contact holes  462 . The line B-B′ is taken to show a section that includes the bonding portion  461  and the contact holes  462 . The line C-C′ is taken to show a section that only includes the wiring portion  463  and does not include the contact holes  462  and the bonding portion  461 . 
       FIGS. 19A through 19C  are cross-sectional views illustrating the light emitting device of  FIG. 18B  taken along lines A-A′, B-B′, and C-C′. Hereinafter, a detailed description will be made with reference to  FIGS. 17, 18A, 18B, and 19A through 19C . 
     In  FIG. 19A , each of the contact holes  462  extends from the first electrode layer  440  to the inside of the second conductivity type semiconductor layer  410 . The contact holes  462  pass through the first conductivity type semiconductor layer  430  and the active layer  420  and extend to the second conductivity type semiconductor layer  410 . The contact holes  462  extend at least to part of the second conductivity type semiconductor layer  410 . However, the contact holes  462  do not necessarily extend to the surface of the second conductivity type semiconductor layer  410 . However, since the contact holes  462  are used for current spreading in the second conductivity type semiconductor layer  410 , the contact holes  462  need to extend to the second conductivity type semiconductor layer  410 . 
     The contact hole  462  needs to have a predetermined area to spread the current in the second conductivity type semiconductor layer  410 . Contrary to the bonding portion  461 , the contact hole  462  is not used for an electrical connection. Therefore, the contact holes  462  are formed in a predetermined number so that each contact hole  462  has an area small enough to allow for uniform current spreading in the second conductivity type semiconductor layer  410 . A small number of contact holes  462  may cause deterioration in electrical characteristics due to non-uniform current spreading. A large number of contact holes  462  may cause difficulty in the process of forming the contact holes  462  and a decrease in a light emitting area due to a decrease in the area of the active layer. Therefore, the number of contact holes  462  may be appropriately determined in considerations of these facts. Each of the contact holes  462  is formed to have as small an area as possible and allow for uniform current spreading. 
     The plurality of contact holes  462  may be formed for current spreading. Also, the contact hole  462  may have a cylindrical shape. A cross section of the contact hole  462  may be smaller than that of the bonding portion  461 . Further, the contact hole  462  may be separated from the bonding portion  461  by a predetermined distance. The contact holes  462  and the bonding portion  461  may be connected to each other in the first electrode structure  440  by the wiring portion  463  to be described below. For this reason, the contact holes  462  are separated from the bonding portion  461  by the predetermined distance, and thus induce uniform current spreading in the first conductivity type semiconductor layer  430 . 
     The contact holes  462  are formed from the first electrode structure  440  to the inside of the second conductivity type semiconductor layer  410 . Since the contact holes  462  are formed to spread the current in the second conductivity type semiconductor layer  410 , the contact holes  462  need to be electrically separated from the first conductivity type semiconductor layer  430  and the active layer  420 . Accordingly, the contact holes  462  are electrically separated from the first electrode structure  440 , the first conductivity type semiconductor layer  430 , and the active layer  420 . Electrical separation may be achieved by using an insulating material such as a dielectric. 
     In  FIG. 19B , the bonding portion  461  starts from the first electrode structure  440 , passes through the first conductivity type semiconductor layer  430 , the active layer  420  and the second conductivity type semiconductor layer  410 , and extends to the surface of the second conductivity type semiconductor layer  410 . Since the bonding portion  461  is connected from the first surface of the light emitting stack  430 ,  420 ,  410  to at least one of the plurality of contact holes  462 . A region of the bonding portion  461  that is exposed at the first surface is provided as a bonding region. 
     Particularly, since the bonding portion  461  is formed to connect the second electrode structure  460  to an external current source (not shown), at least one bonding portion  461  needs to be included in the second electrode structure  460 . 
     Since the bonding portion  461  is electrically connected to the external current source on the surface of the second conductivity type semiconductor layer  410  to supply current to the contact holes  462 , the bonding portion  461  may be electrically separated from the first electrode structure  440 , the second conductivity type semiconductor layer  410 , and the active layer  420 . Electrical separation may be achieved by forming an insulating layer using an insulating material such as a dielectric. 
     The bonding portion  461  supplies current to the contact holes  462 . Further, the bonding portion  461  may be formed so that the bonding portion  461  is not electrically separated from the second conductivity type semiconductor layer  410  so as to directly spread the current. The bonding portion  461  may be electrically separated from the second conductivity type semiconductor layer  410  or not, according to whether current supply to the contact holes  462  or current spreading in the second conductivity type semiconductor layer  410  is required. 
     The cross section of the bonding portion  461  at the active layer  420  may be smaller than that of the bonding portion  461  at the surface of the second conductivity type semiconductor layer  410 . In this way, the area of the active layer  420  is maximized as much as possible in order to ensure an increase in luminous efficiency. However, the bonding portion  461  at the surface of the second conductivity type semiconductor layer  410  needs to have a predetermined area so as to be connected with the external current source. 
     The bonding portion  461  may be located at the center of the light emitting device  400 . In this case, the contact holes  462  are preferably separated from the bonding portion  461  by the predetermined distance, and uniformly distributed. Referring to  FIG. 18A , the bonding portion  461  and the contact holes  462  are uniformly distributed over the second conductivity type semiconductor layer  410  to optimize the current spreading. In  FIG. 18A , it is assumed that there are one bonding portion  461  and eight contact holes  462 . However, the number of bonding portion  461  and the number of contact holes  462  may be appropriately determined in consideration of factors for electrical connection state (e.g. the position of the external current source) and current spreading state (e.g. the thickness of the second conductivity type semiconductor layer  410 ). 
     When the plurality of contact holes  462  are formed, the bonding portion  461  may be directly connected to each of the plurality of contact holes  462 . In this case, the bonding portion  461  is formed at the center of the light emitting device  400 , and the contact holes  462  are formed around the bonding portion  461 . Further, the wiring portion  463  may directly connect the bonding portion  461  and the contact holes  462  in a radial direction. 
     Alternatively, some of the plurality of contact holes  462  may be directly connected to the bonding portion  461 . Other contact holes  462  may be connected to the contact holes  462  that are directly connected to the bonding portion  461 , such that these contact holes  462  are indirectly connected to the bonding portion  461 . In this way, a larger number of contact holes  462  can be formed to thereby increase current spreading efficiency. 
     In  FIGS. 19A through 19C , the wiring portion  463  is formed in the first electrode structure  440  and connects the bonding portion  461  and the contact holes  462  to each other. Therefore, a considerable amount of the first electrode structure  440  is located at a rear surface opposite to the direction in which light is emitted from the active layer  420 , thereby increasing luminous efficiency. Particularly, in  FIG. 19C , only the wiring portion  463  is located in the first electrode structure  440 . The second electrode structure  460  is not located at the first conductivity type semiconductor layer  430 , the active layer  420 , and the second conductivity type semiconductor layer  410 . Accordingly, as shown in  FIG. 19C , the bonding portion  461  and the contact holes  462  do not affect light emission, so they have higher luminous efficiency. 
     The wiring portion  463  is electrically separated from the first electrode structure  440 . The second electrode structure  460  and the first electrode structure  440  include electrodes that have polarities opposite to each other to supply external power to the second conductivity type semiconductor layer  410  and the first conductivity type semiconductor layer  430 , respectively. Therefore, the two electrodes must be electrically separated from each other. Electrical separation may be achieved by forming an insulating layer  480  using an insulating material, such as a dielectric. 
     In  FIG. 19B , since the bonding portion  461  is located on the surface of the second conductivity type semiconductor layer  410 , it is possible to obtain the characteristics of a vertical light emitting device. In  FIG. 19C , since the wiring portion  463  is located in the same plane as the first electrode structure  440 , it is possible to obtain the characteristics of a horizontal light emitting device. Therefore, the light emitting device  400  has a structure in which the horizontal light emitting device and the vertical light emitting device are integrated. 
     Referring to  FIGS. 19A through 19C , the first conductivity type semiconductor layer  430  may be a p-type semiconductor layer, and the first electrode structure  440  may be a p-type electrode part. In this case, the second conductivity type semiconductor layer  410  may be an n-type semiconductor layer, and the second electrode structure  460  may be an n-type electrode. The second electrode structure  460  includes the bonding portion  461 , the contact holes  462 , and the wiring portion  463  that are connected to each other. When the second electrode part  460  is formed of the n-type electrode, the second electrode structure  460  may be electrically separated from the first electrode structure  440  formed of the p-type electrode by the insulating layer  480  that is formed of an insulating material. 
       FIG. 20  illustrates the light emission of a light emitting device having an uneven pattern formed on the surface thereof according to an exemplary embodiment of the present invention. The light emitting device according to this embodiment includes the second conductivity type semiconductor layer  410  that forms an outermost surface in a direction where emitted light moves. Accordingly, it is easy to form an uneven pattern on the surface by using a well-known method, such as photolithography. In this case, light emitted from the active layer  420  passes through an uneven pattern  490  that is formed on the surface of the second conductivity type semiconductor layer  410 , and then the light is extracted. The uneven pattern  490  increases light extraction efficiency. 
     The uneven pattern  490  may have a photonic crystal structure. Photonic crystals contain different media with different refractivity in which the media are regularly arranged in a crystal-like manner. The photonic crystals may increase light extraction efficiency by controlling light in unit of length corresponding to a multiple of a wavelength of light. The photonic crystal structure may be formed according to an appropriate process after forming the second conductivity type semiconductor layer  410  and the first electrode structure  460 . For example, the photonic crystal structure may be formed by an etching process. 
     When the uneven pattern  490  is formed on the second conductivity type semiconductor layer  410 , the barrier portion  470  preferably extends to the inside of the second conductivity type semiconductor layer  410 , not the surface thereof. The barrier portion  470  does not adversely affect the light extraction efficiency improved by the uneven pattern  490  and separates a light emitting region into a plurality of light emitting regions. 
     A semiconductor light emitting device according to another exemplary embodiment of the present invention will be described with reference to  FIGS. 21 through 25 . 
       FIG. 21  is a perspective view illustrating a semiconductor light emitting device according to another exemplary embodiment of the invention.  FIG. 22  is a plan view illustrating the semiconductor light emitting device of  FIG. 21 . Hereinafter, a detailed description will be made with reference to  FIGS. 21 and 22 . 
     A semiconductor light emitting device  500  according to this embodiment includes a first conductivity type semiconductor layer  511 , an active layer  512 , a second conductivity type semiconductor layer  513 , a second electrode layer  520 , a first insulating layer  530 , a first electrode layer  540 , and a conductive substrate  550  that are sequentially stacked. Here, the second electrode layer  520  includes a region where a portion of an interface in contact with the second conductivity type semiconductor layer  513  is exposed. The first electrode layer  540  includes at least one contact hole  541 . The contact hole  541  is electrically connected to the first conductivity type semiconductor layer  511 , electrically insulated from the second conductivity type semiconductor layer  513  and the active layer  512 , and extends from one surface of the first electrode layer  540  to at least part of the first conductivity type semiconductor layer  511 . 
     In the semiconductor light emitting device  500 , the first conductivity type semiconductor layer  511 , the active layer  512 , and the second conductivity type semiconductor layer  513  perform light emission. Hereinafter, they are referred to as a light emitting stack  510 . That is, the semiconductor light emitting device  500  includes the light emitting stack  510 , the first electrode layer  540 , the second electrode layer  520  and the first insulating layer  530 . The first electrode layer  540  is electrically connected to the first conductivity type semiconductor layer  511 . The second electrode layer  520  is electrically connected to the second conductivity type semiconductor layer  513 . The first insulating layer  530  electrically insulates the electrode layers  520  and  540  from each other. Further, the conductive substrate  550  is included as a substrate to grow or support the semiconductor light emitting device  500 . 
     Each of the semiconductor layers  511  and  513  may include a semiconductor such as a GaN-based semiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, a GaP-based semiconductor, and a GaAsP-based semiconductor. The semiconductor layers may be formed by using, for example, molecular beam epitaxy (MBE). In addition, each of the semiconductor layers  511  and  513  may be formed of any one of semiconductors, such as a group Ill-V semiconductor, a group II-VI semiconductor and Si. Each of the semiconductor layers  511  and  513  is formed by doping the above-described semiconductor with appropriate impurities in consideration of the conductivity type. 
     The active layer  512  is a layer where light emission is activated. The active layer  320  may be formed of a material having a smaller energy band gap than each of the first and second conductivity type semiconductor layers  511  and  513 . For example, when the first and second conductivity type semiconductor layers  511  and  513  may be a GaN-based compound semiconductor, the active layer  512  may be formed by using an InAlGaN-based compound semiconductor that has a smaller energy bandgap than GaN. That is, the active layer  512  may include In x Al y Ga (1-x-y) N (where 0≤x≤1, 0≤y≤1, and 0≤x+y≤1 are satisfied). 
     Here, in consideration of characteristics of the active layer  512 , the active layer  512  is preferably not doped with impurities. A wavelength of emitted light may be controlled by adjusting a mole ratio of constituents. Therefore, the semiconductor light emitting device  500  may emit any one of infrared light, visible light, and UV light according to the characteristics of the active layer  512 . 
     Each of the electrode layers  520  and  540  is formed in order to apply voltage to the same conductivity type semiconductor layer. Therefore, in consideration of electroconductivity, the electrode layers  520  and  540  may be formed of metal. That is, the electrode layers  520  and  540  include electrodes that electrically connect the semiconductor layers  511  and  513  to an external current source (not shown). The electrode layers  520  and  540  may include, for example, Ti as an n-type electrode, and Pd or Au as a p-type electrode. 
     The first electrode layer  540  is connected to the first conductivity type semiconductor layer  511 , and the second electrode layer  520  is connected to the second conductivity type semiconductor layer  513 . That is, since the first and second electrode layers  540  and  520  are connected to the different conductivity type semiconductor layers from each other, the first and second layers  540  and  520  are electrically separated from each other by the first insulating layer  530 . The first insulating layer  530  may be formed of a material having low electroconductivity. The first insulating layer  530  may include, for example, an oxide such as SiO 2 . 
     The second electrode layer  520  may reflect light generated from the active layer  512 . Since the second electrode layer  520  is located below the active layer  512 , the second electrode layer  520  is located at a surface opposite to a direction, in which the semiconductor light emitting device  500  emits light, on the basis of the active layer  512 . Light moving from the active layer  512  to the second electrode layer  520  is opposite to the light emitting direction of the semiconductor light emitting device  500 , and thus the light moving toward the second electrode layer  520  needs to be reflected to increase luminous efficiency. Therefore, when the second electrode layer  520  has light reflectivity, the reflected light moves toward a light emitting surface to thereby increase the luminous efficiency of the semiconductor light emitting device  500 . 
     In order to reflect the light generated from the active layer  512 , the second electrode layer  520  may be formed of metal that appears white in a visible light region. For example, the white metal may be any one of Ag, Al, and Pt. 
     The second electrode layer  520  includes a region where a portion of the interface in contact with the second conductivity type semiconductor layer  513  is exposed. A lower surface of the first electrode layer  540  is in contact with the conductive substrate  550 , and the first electrode layer  540  is electrically connected to an external current source (not shown) through the conductive substrate  550 . However, the second electrode layer  520  requires a separate connecting region so as to be connected to the external current source. Therefore, the second electrode layer  520  includes an area that is exposed by partially etching the light emitting stack  510 . 
     In  FIG. 21 , an example of a via hole  514  is shown. The via hole  514  is formed by etching the center of the light emitting stack  510  to form an exposed region of the second electrode layer  520 . An electrode pad portion  560  may be further formed at the exposed region of the second electrode layer  520 . The second electrode layer  520  may be electrically connected to the external power source by the exposed region thereof. At this time, the second electrode layer  520  is electrically connected to the external power source by using the electrode pad portion  560 . The second electrode layer  520  may be electrically connected to the external current source by a wire or the like. For convenient connection to the external current source, the diameter of the via hole preferably increases from the second electrode layer toward the first conductivity type semiconductor layer. 
     The via hole  514  is formed by selective etching. In general, the light emitting stack  510  including the semiconductors is only etched, and the second electrode layer  520  including the metal is not etched. The diameter of the via hole  514  may be appropriately determined by those skilled in the art in consideration of the light emitting area, electrical connection efficiency, and current spreading in the second electrode layer  520 . 
     The first electrode layer  540  includes at least one contact hole  541 . The contact hole  541  is electrically connected to the first conductivity type semiconductor layer  511 , electrically insulated from the second conductivity type semiconductor layer  513  and the active layer  512 , and extends to at least part of the first conductivity type semiconductor layer  511 . The first electrode layer  540  includes at least one contact hole  541  in order to connect the first conductivity type semiconductor layer  511  to the external current source. The contact hole  541  penetrates the second electrode layer  520  between the first electrode layer  540  and the second conductivity type semiconductor layer  513 , the second conductivity type semiconductor layer  513 , and the active layer  512 , and extends to the first conductivity type semiconductor layer  511 . Further, the contact hole  541  is formed of an electrode material. 
     When the contact hole  541  is only used for the electrical connection, the first electrode layer  540  may include one contact hole  541 . However, in order to uniformly spread current that is transmitted to the first conductivity type semiconductor layer  511 , the first electrode layer  540  may include a plurality of contact holes  541  at predetermined positions. 
     The conductive substrate  550  is formed in contact with and is electrically connected to the first electrode layer  540 . The conductive substrate  550  may be a metallic substrate or a semiconductor substrate. When the conductive substrate  550  is the metallic substrate, the conductive substrate  550  may be formed of any one of Au, Ni, Cu, and W. Further, when the conductive substrate  550  is the semiconductor substrate, the conductive substrate  550  may be formed of any one of Si, Ge, and GaAs. The conductive substrate  550  may be a growth substrate. Alternatively, the conductive substrate  550  may be a support substrate. After a non-conductive substrate, such as a sapphire substrate, having relatively small lattice-mismatching is used as a growth substrate, the non-conductive substrate is removed, and the support substrate is bonded. 
     Also, when the conductive substrate  550  is the support substrate, the conductive substrate  550  may be formed by a plating method or a substrate bonding method. As a method of forming the conductive substrate  550  in the semiconductor light emitting device  500 , the plating method of forming a plating seed layer to form a substrate or the substrate bonding method of separately preparing the conductive substrate  550  and bonding the conductive substrate  550  by using a conductive adhesive, such as Au, Au—Sn, and Pb—Sr may be used. 
       FIG. 22  is a plan view illustrating the semiconductor light emitting device  500 . The via hole  514  is formed in the top surface of the semiconductor light emitting device  500 , and the electrode pad portion  560  is located at the exposed region of the second electrode layer  520 . In addition, though not shown in the top surface of the semiconductor light emitting device  500 , the contact holes  541  are shown as a dotted line in order to display the positions of the contact holes  541 . The first insulating layer  530  may extend and surround the contact hole  541  so that the contact hole  541  is electrically separated from the second electrode layer  520 , the second conductivity type semiconductor layer  513 , and the active layer  512 . This will be described in more detail with reference to  FIGS. 23B and 23C . 
       FIGS. 23A through 23C  are cross-sectional views of the semiconductor light emitting device shown in  FIG. 22  taken along the lines A-A′, B-B′, and C-C′. The line A-A′ is taken to show a cross section of the semiconductor light emitting device  500 . The line B-B′ is taken to show a cross section that includes the contact holes  541  and the via hole  514 . The line C-C′ is taken to show a cross section that only includes the contact holes  541 . Hereinafter, the description will be made with reference to  FIGS. 21 through 23C . 
     Referring to  FIG. 23A , neither the contact hole  541  nor the via hole  514  is shown. Since the contact hole  541  is not connected by using a separate connecting line but is electrically connected by the first electrode layer  540 , the contact hole  541  is not shown in the cross section in  FIG. 23 . 
     Referring to  FIGS. 23B and 23C , the contact hole  541  extends from the interface between the first electrode layer  540  and the second electrode layer  520  to the inside of the first conductivity type semiconductor layer  511 . The contact hole  541  passes through the second conductivity type semiconductor layer  513  and the active layer  512  and extends to the first conductivity type semiconductor layer  511 . The contact hole  541  extends at least to the interface between the active layer  512  and the first conductivity type semiconductor layer  511 . Preferably, the contact hole  541  may extend to part of the first conductivity type semiconductor layer  511 . However, the contact hole  541  is used for the electrical connection and current spreading. Once the contact hole  541  is in contact with the first conductivity type semiconductor layer  511 , the contact hole  541  does not need to extend to the outer surface of the first conductivity type semiconductor layer  511 . 
     The contact hole  541  needs to have a predetermined area in order to spread current in the first conductivity type semiconductor layer  511 . A predetermined number of contact holes  541  may be provided, and may each have an area small enough to allow for uniform current spreading in the first conductivity type semiconductor layer  511 . The number of contact holes may be appropriately selected in due consideration of the fact that a small number of contact holes  541  deteriorate electrical characteristics due to non-uniform current spreading, while a large number of contact holes  541  cause difficulties in the formation process thereof and cause a reduction in a light emitting area due to a decrease in the area of the active layer. Each of the contact holes  541  is realized so as to have as small an area as possible yet retain a shape effective for current spreading. The contact hole  541  extends from the second electrode layer  520  into the first conductivity type semiconductor layer  511 . Since the contact hole  541  is used for the current spreading in the first conductivity type semiconductor layer, the contact hole  541  needs to be electrically separated from the second conductivity type semiconductor layer  513  and the active layer  512 . Therefore, the contact hole  541  may be electrically separated from the second electrode layer  520 , the second conductivity type semiconductor layer  513  and the active layer  512 . Accordingly, the first insulating layer  530  may extend to surround the circumference of the contact hole  530 . This electrical separation may be performed by using an insulating material such as a dielectric. 
     In  FIG. 23B , the exposed region of the second electrode layer  520  serves as an electrical connection point for an external power source (not shown) of the second electrode layer  520 . The electrode pad portion  560  may be placed on the exposed region. Here, the second insulating layer  570  is formed on the inner side surface of the via hole  514  to thereby electrically separate the multilayer laminate structure  510  and the electrode pad portion  560 . 
     Referring to  FIG. 23A , the first electrode layer  540  and the second electrode layer  520  are formed on the same layer, so that the semiconductor light emitting device  500  has the characteristics of a horizontal semiconductor light emitting device. Referring to  FIG. 23B , the electrode pad portion  560  is placed on the surface of the second electrode layer  520 , so that the semiconductor light emitting device  500  may have the characteristics of a vertical light emitting device. Consequently, the semiconductor light emitting device  500  has a combination structure having the characteristics of both vertical and horizontal semiconductor light emitting devices. 
     In  FIGS. 23A and 23C , the first conductivity type semiconductor layer  511  is an n-type semiconductor layer, and the first electrode layer  540  may be an n-type electrode. In this case, the second conductivity type semiconductor layer  513  may be a p-type semiconductor layer, and the second electrode layer  520  may be a p-type electrode. Thus, the first electrode layer  540 , the n-type electrode, and the second electrode layer  520 , the p-type electrode, may be electrically insulated from each other by the first insulating layer  530  provided therebetween. 
       FIG. 24  illustrates light emission in a semiconductor light emitting device having an uneven pattern on the surface thereof, according to this embodiment. A description of the previously described elements will be omitted. 
     The outermost layer of the semiconductor light emitting device  500 , in a direction in which emitted light moves, is the first conductivity type semiconductor layer  511 . Thus, the uneven pattern  580  may be easily formed on the surface by using a method known in the art such as a photolithography method. In this case, light emitted from the active layer  512  is extracted through the uneven pattern  580  formed on the surface of the first conductivity type semiconductor layer  511 , thereby enhancing light extraction efficiency. 
     The uneven pattern may be a photonic crystal structure. Photonic crystals refer to media having different refractive indices that are regularly arranged like crystals. The photonic crystals can increase light extraction efficiency by controlling light in the unit of length corresponding to a multiple of a wavelength of light. 
       FIG. 25  illustrates a second electrode layer exposed on a corner portion in the semiconductor light emitting device according to this embodiment. 
     According to another aspect of the present invention, a method of manufacturing a semiconductor light emitting device includes: sequentially stacking a first conductivity type semiconductor layer  511 ′, an active layer  512 ′, a second conductivity type semiconductor layer  513 ′, a second electrode layer  520 ′, an insulating layer  530 ′, a first electrode layer  540 ′, and a conductive substrate  550 ′; forming an exposed region in a part of the interface of the second electrode layer  520 ′ with the second conductivity type semiconductor layer  513 ′; and forming at least one contact hole  541 ′ extending from one surface of the first electrode layer  540 ′ to at least a part of the first conductivity type semiconductor layer  511 ′ and electrically insulated from the second conductivity type semiconductor layer  513 ′ and the active layer  512 ′, such that the first electrode layer  540 ′ is electrically connected with the first conductivity type semiconductor layer  511 ′. 
     The exposed region of the second electrode layer  520 ′ may be provided by forming the via hole  510 ′ in the light emitting stack  510 ′ (see  FIG. 21 ), or by mesa-etching the light emitting stack  510 ′ (see  FIG. 25 ). In this embodiment, a description of the same elements as those of the embodiment depicted in  FIG. 21  will be omitted in the interest of clarity. 
     Referring to  FIG. 25 , one corner of the semiconductor light emitting device  500 ′ is mesa-etched. The etching is performed on the light emitting stack  510 ′ so as to expose the second electrode layer  520 ′ at the interface with the second conductivity type semiconductor layer  513 ′. The exposed region of the second electrode layer  520 ′ is formed at the corner of the semiconductor light emitting device  500 ′. The process of forming the exposed region at the corner is a simpler process than the process of forming the via hole, and may facilitate a subsequent electrical connection process. 
     Referring to  FIGS. 26 through 36 , a semiconductor light emitting device according to another exemplary embodiment of the present invention will now be described. 
       FIG. 26  is a schematic perspective view illustrating a semiconductor light emitting device according to this embodiment.  FIG. 27  is a top plan view illustrating the semiconductor light emitting device depicted in  FIG. 26 , and  FIG. 28  is a cross-sectional view taken along line A-A′, illustrating the semiconductor light emitting device depicted in  FIG. 27 . Hereinafter, a description will be made with reference to  FIGS. 26 through 28 . 
     A semiconductor light emitting device  600 , according to this embodiment, includes a first conductivity type semiconductor layer  611 , an active layer  612 , a second conductivity type semiconductor layer  613 , a second electrode layer  620 , an insulating layer  630 , a first electrode layer  640  and a conductive substrate  650  that are sequentially stacked. Here, in order to be electrically connected with the first conductivity type semiconductor layer  611 , the first electrode layer  640  includes at least one contact hole  641 . Here, the at least one contact hole  641  extends from one surface of the first electrode layer  640  up to at least a part of the first conductivity type semiconductor layer  611 , and is electrically insulated from the second conductivity type semiconductor layer  613  and the active layer  612 . The first electrode layer  640  is not an essential element in this embodiment. Although not shown, the first electrode layer may not be included, and the contact hole  641  may be formed from one surface of the conductive substrate. That is, to be electrically connected with the first conductivity type semiconductor layer  111 , the conductive substrate  650  may include at least one contact hole  641  extending from one surface of the conductive substrate  650  up to at least a part of the first conductivity type semiconductor layer  611  and electrically insulated from the second conductivity type semiconductor layer  113  and the active layer  112 . Here, the conductive substrate is electrically connected to an external power source (not shown), and the first conductivity type semiconductor layer receives voltage through the conductive substrate. 
     The second electrode layer  620  has an exposed region  614  that is formed on a part of its interface with the second conductivity type semiconductor layer  613  by etching the first conductivity type semiconductor layer  611 , the active layer  612  and the second conductivity type semiconductor layer  613 . An etch stop layer  621  is formed on the exposed region  614 . 
     The light emission of the semiconductor light emitting device  600  is carried out by the first conductivity type semiconductor layer  611 , the active layer  612 , and the second conductivity type semiconductor layer  613 , and thus they are referred to as a light emitting stack  610 . That is, the semiconductor light emitting device  600  includes the light emitting stack  610 , the first electrode layer  640  electrically connected with the first conductivity type semiconductor layer  611  by the contact hole  641 , the second electrode layer  620  electrically connected with the second conductivity type semiconductor layer  613 , and the insulating layer  630  electrically insulating the electrode layers  620  and  640 . In addition, the conductive substrate  650  is provided to support the semiconductor light emitting device  600 . 
     The first conductivity type semiconductor layer  611  and the second conductivity type semiconductor layer  613  may include, for example, a semiconductor material such as a GaN-based semiconductor, a ZnO-based semiconductor, a GaAs-based semiconductor, a GaP-based semiconductor, or a GaAsP-based semiconductor; however, the semiconductor layers  611  and  613  are not limited thereto. The semiconductor layers  611  and  613  may also be formed of a material appropriately selected from the group consisting of group III-V semiconductors, group II-VI semiconductors, and Si. In addition, the semiconductor layers  611  and  613  may be doped with n-type impurities or p-type impurities in consideration of the conductivity type of each of the semiconductors described above. 
     The active layer  612  activates light emission, and is formed of a material having a smaller energy band gap than the energy band gaps of the first conductivity type semiconductor layer  611  and the second conductivity type semiconductor layer  613 . For example, when the first conductivity type semiconductor layer  611  and the second conductivity type semiconductor layer  613  are GaN-based compound semiconductors, the active layer  612  may be formed by using an InAlGaN-based compound semiconductor having a smaller energy band gap than that of GaN. That is, the active layer  612  may include In x Al y Ga (1-x-y) N (0≤x≤1, 0≤y≤1, 0≤x+y≤1). 
     Here, the active layer  612  may not be doped with impurities due to the characteristics of the active layer  612 , and the wavelength of emitted light can be regulated by controlling the mole ratio of materials. Accordingly, the semiconductor light emitting device  600  can emit infrared light, visible light or ultraviolet light depending on the characteristic of the active layer  612 . 
     The first electrode layer  640  and the second electrode layer  620  serve to supply voltage to the semiconductor layers of the same conductivity type, respectively. The semiconductor layers  611  and  613  are electrically connected with an external power source (not shown) by the electrode layers  620  and  640 . 
     The first electrode layer  640  is connected with the first conductivity type semiconductor layer  611 , and the second electrode layer  620  is connected with the second conductivity type semiconductor layer  613 . Thus, the first electrode layer  640  and the second electrode layer  620  are electrically separated from each other by the first insulating layer  630 . The first insulating layer  630  may be formed of a material having a low level of electric conductivity, for example, an oxide such as SiO 2 . 
     To be electrically connected with the first conductivity type semiconductor layer  611 , the first electrode layer  640  includes at least one contact hole  641  extending up to a part of the first conductivity type semiconductor layer  611  and electrically insulated from the second conductivity type semiconductor layer  613  and the active layer  612 . Here, this electrical insulation may be made by the extension of the insulating layer  630  placed between the first and second electrode layers. The contact hole  641  extends to the first conductivity type semiconductor layer  611  through the second electrode layer  620 , the insulating layer  630  and the active layer  612 , and has an electrode material therein. The first electrode layer  640  is electrically connected with the first conductivity type semiconductor layer  611  by the contact hole  641 , thereby connecting the first conductivity type semiconductor layer  611  to an external power source (not shown). 
     In the event that the contact hole  641  is formed only for an electrical connection with the first conductivity type semiconductor layer  611 , the first electrode layer  640  may have a single contact hole  641 . However, the first electrode layer  640  may include one or more contact holes  641  at predetermined locations in order to ensure uniform current spreading in the first conductivity type semiconductor layer  611 . 
     The second electrode layer  620  is placed under the active layer  612 , on the opposite side to a direction that light is emitted from the semiconductor light emitting device  600  with reference to the active layer  612 . Accordingly, light moving toward the second electrode layer  620  is reflected, and this enhances luminous efficiency. 
     The second electrode layer  620  may be formed of a white metal in a visible light region in order to reflect light generated from the active layer  612 . For example, the second electrode layer  620  may include at least one of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt and Au. 
     The second electrode layer  620  has an exposed portion at its interface with the second conductivity type semiconductor layer  613 . This exposed portion is formed by etching the first conductivity type semiconductor layer  611 , the active layer  612  and the second conductivity type semiconductor layer  613 . The etch stop layer  621  is formed on the exposed region  614 . The first electrode layer  640 , in contact with the conductive substrate  650  placed thereunder, can be connected with an external power source, whereas the second electrode layer  620  requires a separate connection region for a connection with the external power source (not shown). Therefore, the second electrode layer  620  has the exposed region  614  on a part of its interface with the second conductivity type semiconductor layer  613  by etching a portion of the light emitting stack  610 . In this manner, the second conductivity type semiconductor layer  613  is connected to the external power source (not shown) by the second electrode layer  620 . 
     The area of the exposed region  614  may be appropriately selected by those skilled in the art in consideration of a light emitting area, electrical connection efficiency and current spreading in the second electrode layer  620 .  FIGS. 27 through 29  illustrate an embodiment in which the exposed region  614  of the second electrode layer  620  is formed at the corner by etching the corner of the light emitting stack  610 . 
     The exposed region  614  is formed by selective etching by which only a part of the light emitting stack  610  is etched while the second electrode layer  620 , typically containing metal, is not etched. However, full control over this selective etching that etches only the part of the light emitting stack  610  is hard to implement. For this reason, the second electrode layer, placed under the light emitting stack  610 , may also be etched in part. The second electrode layer  620 , etched in part, may cause the metallic material of the second electrode layer  620  to bond with the second conductivity type semiconductor layer  613 , resulting in current leakage. Therefore, the etch stop layer  621  is formed on a region where the etching of the light emitting stack  610  is carried out (i.e., the exposed region of the second electrode layer  620 ). 
     The etch-stop layer  621  can prevent the metal, forming the second electrode layer  620 , from being bonded to the side of the light-emitting stack  610 , thereby reducing a leakage current and facilitating etching. The etch-stop layer  621  may be formed of materials used to prevent the etching of the light-emitting stack  600 . Examples of these materials may include insulating materials such as a silicon oxide or a nitride oxide, SiO 2 , SiO x N y , or Si x N y , for example. However, the present invention is not limited thereto. Here, the etch-stop layer  621  is not necessarily formed of insulating materials, and may be formed of conductive materials, which do not have any adverse effect on the operation of the device. Therefore, as long as the etch-stop layer  621  provides etch-stop performance, the etch-stop layer  621  may be appropriately formed of conductive materials. 
     Furthermore, an electrode pad portion  660  may pass through the etch-stop layer  621  and be formed in the exposed region  614 . The electrode pad portion  660  passes through the etch-stop layer  621  and is electrically connected to the second electrode layer. Here, an electrical connection between the second electrode layer  620  and an external power source (not shown) is further facilitated. 
     The conductive substrate  650  is located under the first electrode layer  640 . Further, the conductive substrate  650  comes into contact with the first electrode layer  640  and is electrically connected thereto. The conductive substrate  650  may be a metallic substrate or a semiconductor substrate. The conductive substrate  650  may be formed of a material including any one of Au, Ni, Al, Cu, W, Si, Se, and GaAs, for example, Si—Al alloys. Here, the conductive substrate  650  may be formed by plating or bonding according to the selected material. The conductive substrate  650  may be a support substrate that is bonded after a sapphire substrate with a relatively small mismatch is used as a growth substrate, and is then removed. 
       FIG. 27  is an upper plan view illustrating the semiconductor light emitting device  600 . Though not shown in the upper surface of the semiconductor light emitting device  600 , the contact holes  641  are indicated by dotted lines in order to identify where the contact holes  641  are located. An insulating layer  630  may be extended around the contact holes  641  so that the contact holes  641  are electrically insulated from the second electrode layer  620 , the second conductivity type semiconductor layer  613 , and the active layer  612 . This will be described in detail with reference to  FIG. 28 . 
       FIG. 28  is a cross-sectional view taken along the line A-A′ of the semiconductor light emitting device, shown in  FIG. 27 . The line A-A′ is selected to take in a cross-section including the contact holes  641  and the exposed region  614 . 
     Referring to  FIG. 28 , the contact holes  641  pass through the interface of the first electrode layer  640 , the second electrode layer  620 , the second conductivity type semiconductor layer  613 , and the active layer  612 , and are extended to the inside of the first conductivity type semiconductor layer  611 . The contact holes  641  are extended to at least the active layer  612  and the interface of the first conductivity type semiconductor layer  611 , preferably, to a portion of the first conductivity type semiconductor layer  611 . Here, the contact holes  641  are formed to provide an electrical connection and current spreading for the first conductivity type semiconductor layer  611 , which are achieved when the contact holes  641  come into contact with the first conductivity type semiconductor layer  611 . The contact holes  641  do not have to be extended to the outer surface of the first conductivity type semiconductor layer  611 . 
     The contact holes  641  are formed to achieve current spreading of the first conductivity type semiconductor layer  611  and may have a predetermined area. As for the contact holes  641 , a predetermined number of contact holes, which are as small as possible in order to provide uniform current spreading in the first conductivity type semiconductor layer  611 , may be formed. When an insufficient number of contact holes  641  are formed, it becomes difficult to achieve current spreading, thereby worsening electrical characteristics. On the other hand, when an excessive number of contact holes  641  are formed, processing difficulties in forming the contact holes  641  and a reduction in a light-emitting area due to a reduction in the area of the active layer are caused. Therefore, the number of contact holes  641  may be appropriately selected. Therefore, the contact holes  641  are formed in such a manner that the contact holes  641  have as small an area as possible yet provide effective current spreading. 
     The contact holes  641  are extended from the first electrode layer  640  to the inside of the first conductivity type semiconductor layer  611 . Since the contact holes  641  are formed for the current spreading of the first conductivity type semiconductor layer, the contact holes  641  need to be electrically insulated from the second conductivity type semiconductor layer  613  and the active layer  612 . Therefore, the insulating layer  630  may be extended to surround the contact holes  641 . 
     In  FIG. 28 , the second electrode layer  620  includes the exposed region  614 , which is an exposed portion of the interface between the second conductivity type semiconductor layer  613  and the second electrode layer  620 . The exposed region  614  is formed to provide an electrical connection between the second electrode layer  620  and an external power source (not shown). The etch-stop layer  621  is formed in the exposed region  614 . The exposed region  614  may include the electrode pad portion  660  that passes through the etch-stop layer  621  and is electrically connected to the second electrode layer  620 . Here, the insulating layer  670  may be formed on the inside surface of the exposed region  614  in order to electrically separate the light-emitting stack  610  from the electrode pad portion  660 . 
     In  FIG. 28 , since the first electrode layer  641  and the second electrode layer  620  are located in the same plane, the semiconductor light emitting device  600  has the characteristics of a horizontal type semiconductor light emitting device. Since the electrode pad portion  660  is located on the surface of the first conductivity type semiconductor layer  611 , the semiconductor light emitting device  600  may also have the characteristics of a vertical semiconductor light emitting device. Therefore, the semiconductor light emitting device  600  has a configuration in which the characteristics of both vertical and horizontal type semiconductor light emitting devices are combined. 
       FIGS. 29 through 31  are views illustrating a semiconductor light emitting device according to another exemplary embodiment of the invention.  FIG. 29  is a perspective view illustrating the semiconductor light emitting device.  FIG. 30  is an upper plan view of the semiconductor light emitting device of  FIG. 20 .  FIG. 31  is a cross-sectional view taken along the line A-A′ of the semiconductor light emitting device of  FIG. 30 . 
     As shown in  FIGS. 29 through 31 , a central portion of a light-emitting stack  710  is etched, and an exposed region  714 , which is a portion of the interface between a second electrode layer  720  and a second conductivity type semiconductor layer. A description of components identical to those described above will be omitted in the interest of clarity. Here, an etch-stop layer  721  may be partially removed and may be electrically connected to an external power source (not shown). An electrode pad portion  760  that passes through the etch-stop layer  721  and is electrically connected to the second electrode layer  720  may be included. The etch-stop layer  721  may be connected to the external power source (not shown) using wires. For convenience of explanation, the exposed region  714  increases from a first conductivity type semiconductor layer toward a second electrode layer. 
       FIGS. 32 and 33  are views illustrating a modified embodiment of a semiconductor light emitting device according to an exemplary embodiment of the invention.  FIG. 32  is a perspective view illustrating a semiconductor light emitting device.  FIG. 33  is a side sectional view illustrating a semiconductor light emitting device. Here, an upper plan view of the semiconductor light emitting device is similar to that of  FIG. 27 . Similar to  FIG. 28 ,  FIG. 33  is a cross-sectional view taken along the line A-A′. A description of the same components, having been described above, will be omitted. 
     Referring to  FIGS. 32 and 33 , a light-emitting stack  610 ′ is etched to thereby expose a second electrode layer. An etch-stop layer  621 ′, which is formed on the exposed region, is extended to the sides of a second conductivity type semiconductor layer  613 ′ and an active layer  612 ′. In this way, as described above, while the first conductivity type semiconductor layer  611 ′ is being etched, metallic materials of the second electrode layer can be prevented from being bonded to the semiconductor side, and the active layer  612 ′ can also be protected. 
     Here, a method of manufacturing the above-described semiconductor light emitting device will be omitted. 
       FIGS. 34A through 34D  are cross-sectional views illustrating a method of manufacturing a semiconductor light emitting device according to an exemplary embodiment of the invention. More specifically, a method of manufacturing the semiconductor light emitting device, shown in  FIGS. 26 through 28 , will be described. 
     First, as shown in  FIG. 34A , the first conductivity type semiconductor layer  611 , the active layer  612 , the second conductivity type semiconductor layer  613 , and the second electrode layer  620  are stacked on a non-conductive substrate  680  in a sequential manner. 
     Here, the semiconductor layer and the active layer may be stacked using a known process, such as Metal Organic Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), or Hydride Vapor Phase Epitaxy (HVPE). As for the non-conductive substrate  680 , a sapphire substrate that facilitates the growth of semiconductor layers may be used. 
     The second electrode layer  620  is stacked while the etch-stop layer  621  is formed in a region to be exposed by etching the first conductivity type semiconductor layer  611 , the active layer  612 , and the second conductivity type semiconductor layer  613 . 
     The insulating layer  630  and the conductive substrate  650  are then formed on the second electrode layer  620 . Here, as shown in  FIG. 34B , the first electrode layer  640  may be formed between the insulating layer  630  and the conductive substrate  650 . 
     In order that the conductive substrate  650  is electrically connected to the first conductivity type semiconductor layer  611 , the conductive substrate  650  includes the one or more contact holes  641  that are electrically insulated from the second conductivity type semiconductor layer  613  and the active layer  612  and are extended to a portion of the first conductivity type semiconductor layer  611  from one surface of the conductive substrate  650 . 
     As shown in  FIG. 34A , when the first electrode layer  640  is formed between the insulating layer  630  and the conductive substrate  650 , the contact holes  641  are formed starting from one surface of the first electrode layer  640 . That is, in order that the first electrode layer  640  is electrically connected to the first conductivity type semiconductor layer  611 , the first electrode layer  640  includes one or more contact holes  641  that are electrically insulated from the second conductivity type semiconductor layer  613  and the active layer  612  and are extended from the one surface of the first electrode layer  640  to a portion of the first conductivity type semiconductor layer  611 . 
     Here, as the contact holes  641  are formed for the current spreading of the first conductivity type semiconductor layer  611 , the contact holes  641  need to be electrically insulated from the second conductivity type semiconductor layer  613  and the active layer  612 . Therefore, the insulating layer  630  may be extended to surround the contact holes  641 . 
     As shown in  FIG. 34C , which is a reversed view of  FIG. 34B , the non-conductive substrate  680  is removed, a portion of each of the first conductivity type semiconductor layer  611 , the active layer  612 , and the second conductivity type semiconductor layer  613  is etched to thereby form the exposed region  614  in a portion of the interface between the second electrode layer  620  and the second conductivity type semiconductor layer  613 . 
     The exposed region  614  is formed using selective etching so that the light-emitting stack  610  is partially etched while the second electrode layer  620 , which generally contains a metal, is not selected. 
     As described above, since it is difficult to completely control selective etching to etch a region of the light-emitting stack  610 , the second electrode layer  620 , located under the light-emitting stack  610 , may be partially etched. In this embodiment, the etch-stop layer  621  is formed in a region subjected to etching to thereby facilitate etching, so that the metal of the second electrode layer  620  is prevented from being bonded to the side of the light-emitting stack  610 , thereby reducing a leakage current. 
     As shown in  FIG. 34D , one region of the etch-stop layer  621  may be removed in order to provide an electrical connection between the second electrode layer  620  and the external power source. Here, the electrode pad portion  660  may be formed in a region where the etch-stop layer  621  is removed. Furthermore, in order to electrically insulate the light-emitting stack  610  and the electrode pad portion  660 , the insulating layer  670  may be formed on the inside surface of the light-emitting stack, where etching has been performed. 
       FIGS. 34A through 34D  are views illustrating an example in which one edge of the light-emitting stack  610  is etched, and the exposed region  614  of the second electrode layer  620  is formed in the etched edge. When the central portion of the light-emitting stack  610  is etched, the semiconductor light emitting device, as shown in  FIG. 29 , may be manufactured. 
       FIGS. 35A through 35D  are cross-sectional views illustrating a method of manufacturing a modified embodiment of a semiconductor light emitting device according to an exemplary embodiment of the invention. More specifically, a method of manufacturing the semiconductor light emitting device, shown in  FIGS. 32 and 33 , will be described. A description of the same components, having described above with reference to  FIGS. 34A through 34D , will be omitted. 
     First, as shown in  FIG. 35A , the first conductivity type semiconductor layer  611 ′, the active layer  612 ′, the second conductivity type semiconductor layer  613 ′, and a second electrode layer  620 ′ are stacked on a non-conductive substrate  680 ′ in a sequential manner. 
     The second electrode layer  620 ′ is stacked while the etch-stop layer  621 ′ is formed in a region to be exposed by etching the first conductivity type semiconductor layer  611 ′, the active layer  612 ′, and the second conductivity type semiconductor layer  613 ′. Here, before etching a light-emitting stack  610 ′ in order to form an exposed region  614 ′, as shown in  FIG. 35  C, portions of the second conductivity type semiconductor layer  613 ′, the active layer  612 ′, and the second conductivity type semiconductor layer  613 ′ are primarily etched. The etch-stop layer  621 ′ is extended along the portions exposed by primarily etching the second conductivity type semiconductor layer  613 ′, the active layer  612 ′, and the first conductivity type semiconductor layer  611 ′. 
     Here, as shown in  FIG. 35C , when etching the light-emitting stack  610 ′ in order to form the exposed region  614 ′ in the second electrode layer  620 ′, it is possible to etch only the first conductivity type semiconductor layer  611 ′. Therefore, the active layer can also be protected. 
     As shown in  FIG. 35B , an insulating layer  630 ′, a first electrode layer  640 ′, and a conductive substrate  650 ′ are formed on the second electrode layer  620 ′. 
     Here, in order that the first electrode layer  640 ′ is electrically connected to the first conductivity type semiconductor layer  611 ′, the first electrode layer  640 ′ includes one or more contact holes  641  that are electrically insulated from the second conductivity type semiconductor layer  613 ′ and the active layer  612 ′ and are extended from one surface of the first electrode layer  640 ′ to a portion of the first conductivity type semiconductor layer  611 ′. Here, since the contact holes  641 ′ are formed for the current spreading of the first conductivity type semiconductor layer  611 ′, the contact holes  641 ′ need to be electrically insulated from the second conductivity type semiconductor layer  613 ′ and the active layer  612 ′. Therefore, the insulating layer  630 ′ may be extended to surround the contact holes  641 ′. 
     As shown in  FIG. 35C , which is a reversed view of  FIG. 35B , the exposed region  614 ′ is formed in the second electrode layer  620 ′ to partially expose the interface between the second conductivity type semiconductor layer and the second electrode layer. First, the non-conductive substrate  680 ′ is removed, and the first conductivity type semiconductor layer  611 ′ is etched. As described above, in  FIG. 35C , since the active layer  612 ′ and the second conductivity type semiconductor layer  613 ′ have undergone etching, the exposed region  614 ′ can only be formed by etching the first conductivity type semiconductor layer. 
     As described above, when the light-emitting stack  610 ′ is etched, the etch-stop layer  621 ′ may be formed in the exposed region  614 ′ of the second electrode layer  620 ′, thereby facilitating etching. Furthermore, the first conductivity type semiconductor layer  611 ′ is only etched due to the primary etching, performed as shown in  FIG. 35A , thereby protecting the active layer. 
     As shown in  FIG. 35D , in order to connect the second electrode layer  620 ′ to an external power source, one region of the etch-stop layer  621 ′, which is formed on the exposed region  614 ′, may be removed. Here, an electrode pad portion  660 ′ may be formed on the removed portion of the etch-stop layer  621 ′ so as to be electrically connected to the second electrode layer. Here, unlike the process shown in  FIGS. 34A through 34D , only the first conductivity type semiconductor layer  611 ′ is exposed. Therefore, an insulating layer, which is formed to electrically insulate the electrode pad portion  660 ′ from the second electrode layer  610 ′, is not required. 
     When mounting the semiconductor light emitting devices  600 ,  600 ′, and  700 , according to the exemplary embodiments of the invention, the conductive substrates  650 ,  650 ′, and  750  are each electrically connected to the first lead frame, while the electrode pad portions  660 ,  660 ′, and  760  are each electrically connected to the second lead frame using wires. That is, the mounting process may be performed using die-bonding mixed with wire bonding. That is, since the semiconductor light emitting devices  600 ,  600 ′, and  700  may be mounted using die-bonding mixed with wire bonding, maximum luminance efficiency can be ensured, and the manufacturing process can be performed at relatively low cost. 
       FIG. 36  is a schematic cross-sectional view illustrating another modified embodiment of a semiconductor light emitting device according to an exemplary embodiment of the invention. Referring to  FIG. 36 , like the above-described embodiments, a semiconductor light emitting device  600 ″ according to this modified embodiment includes a first conductivity type semiconductor layer  611 ″, an active layer  612 ″, a second conductivity type semiconductor layer  613 ″, a second electrode layer  620 ″, an insulating layer  630 ″, a first electrode layer  640 ″, a conductive substrate  650 ″, which are stacked in a sequential manner, an etch-stop layer  621 ″, and an electrode pad portion  660 ″. In order that the first electrode layer  640 ″ is electrically connected to the first conductivity type semiconductor layer  611 ″, the first electrode layer  640 ″ includes one or more contact holes  641 ″ that are electrically insulated from the second conductivity type semiconductor layer  613 ″ and the active layer  612 ″ and are extended to a portion of the first conductivity type semiconductor layer  611 ″ from one surface of the first electrode layer  640 ″. In this modified embodiment, a passivation layer  670 ″ having an uneven structure is added. Since components, which are described in the same terms, have been described in the above-described embodiment, only the passivation layer  670 ″ will be described. 
     When a configuration having the first conductivity type semiconductor layer  611 ″, the active layer  612 ″, and the second conductivity type semiconductor layer  613 ″ are defined as a light-emitting structure, the passivation layer  670 ″ is formed to cover the sides of the light-emitting structure, thereby protecting the active layer  612 ″ in particular. Here, as shown in  FIG. 36 , the passivation layer  670 ″ may be formed on the top surface as well as the side surfaces of the light-emitting structure, and may also be formed on the upper surface of the etch-stop layer  621 ″. 
     The passivation layer  670 ″ may be formed of a silicon oxide, such as SiO 2 , or a silicon nitride, such as Si x N y , in order to perform a protective function for the light-emitting structure. The passive layer  670 ″ may have a thickness of approximately 0.1 to 2 μm and a corresponding refractive index of approximately 1.4 to 2.0. It may be difficult for light from the active layer  612 ″ to be emitted to the outside due to the difference in refractive index between the passivation layer  670 ″ and air or a molding structure of a package. In this embodiment, the uneven structure is formed on the passivation layer  670 ″ to thereby improve external light extraction efficiency. In particular, as shown in  FIG. 36 , when the uneven structure is formed on a region through which light emitted in a lateral direction of the light active layer  612 ″ passes, the amount of light emitted from the sides of the semiconductor light emitting device  600 ″ can be increased. Specifically, according to simulation results, a semiconductor light emitting device according to this embodiment has increased light extraction efficiency by approximately 5% or higher than a semiconductor light emitting device having the same components except for the passivation layer  670 ″ having the uneven structure. Though not necessarily required in this embodiment, the uneven structure of the passivation layer  670 ″ may also be formed on the upper surface of the first conductivity type semiconductor layer  611 ″ to thereby increase light extraction efficiency in a vertical direction, and may also be formed on the side of the passivation layer  670 ″. 
     A semiconductor light emitting device according to another exemplary embodiment of the invention will be described with  FIGS. 37 through 57 . 
       FIG. 37  is a perspective view schematically illustrating a semiconductor light emitting device according to an exemplary embodiment of the invention.  FIG. 38  is a schematic plan view illustrating the semiconductor light emitting device of  FIG. 37  as viewed from the top side thereof.  FIG. 39  is a schematic sectional view taken along the line A-A′, as shown in  FIG. 38 , of the semiconductor light emitting device of  FIG. 37 . Referring to  FIGS. 37 through 39 , in a semiconductor light emitting device  800  according to this embodiment, a first conductive contact layer  804  is formed on a conductive substrate  807 , and a light-emitting structure, that is, a first conductivity type semiconductor layer  803 , an active layer  802 , and a second conductivity type semiconductor layer  801  are formed on the first conductive contact layer  804 . A high-resistance portion  808  is formed on the sides of the light-emitting structure. As described below, the high-resistance portion  808  may be formed by injecting ions into the sides of the light-emitting structure. The first conductive contact layer  804  is electrically insulated from the conductive substrate  807 . To this end, an insulator  806  is interposed between the first conductive contact layer  804  and the conductive substrate  807 . 
     In this embodiment, the first and second conductivity type semiconductor layers  803  and  801  may be p-type and n-type semiconductor layers, respectively, and may be formed of nitride semiconductors. Therefore, in this embodiment, first conductive and second conductive may mean p-type and n-type, respectively. The invention is not limited thereto, however. The first and conductive semiconductor layers  803  and  801  may satisfy an equation of AlxInyGa(1-x-y)N (where 0≤x≤1, 0≤y≤1, and 0≤x+y≤1 are satisfied), for example, GaN, AlGaN, and InGaN. The active layer  802 , formed between the first and conductive semiconductor layers  803  and  801 , emits light having a predetermined amount of energy by electron-hole recombination and may have a multiple quantum well (MQW) structure in which quantum well layers and quantum barrier layers alternate with each other. As for the multiple quantum well structure, an InGaN/GaN structure may be used. 
     The first conductive contact layer  804  may reflect light, emitted from the active layer  802 , upward from the semiconductor light emitting device  800 , that is, toward the second conductivity type semiconductor layer  801 . Further, the first conductive contact layer  804  and the first conductivity type semiconductor layer  803  may form ohmic contacts. In consideration of these functions, the first conductive contact layer  804  may contain Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, or Au. Here, though not illustrated in detail, the first conductive contact layer  804  may have a dual or multi-layered structure to thereby increase reflection efficiency. For example, the first conductive contact layer  804  may have a structure of Ni/Ag, Zn/Ag, Ni/Al, Zn/Al, Pd/Ag, Pd/Al, Ir/Ag, Ir/Au, Pt/Ag, Pt/Al, or Ni/Ag/Pt. In this embodiment, a portion of the first conductive contact layer  804  may be exposed to the outside. As shown in the drawings, the light-emitting structure may not be formed on the exposed portion. The exposed portion of the first conductive contact layer  804  corresponds to an electrical connection portion to which an electrical signal is applied. An electrode pad  805  may be formed on the exposed portion thereof. 
     As described below, the conductive substrate  807  serves as a support that holds the light-emitting structure during a laser-lift off process and may be formed of a material containing any one of Au, Ni, Al, Cu, W, Si, Se, and GaAs, for example, Si—Al alloys. Here, according to the selected material, the conductive substrate  807  may be formed using plating or bonding. In this embodiment, the conductive substrate  807  is electrically connected to the second conductivity type semiconductor layer  801 , so that an electrical signal may be applied to the second conductivity type semiconductor layer  801  through the conductive substrate  807 . To this end, as shown in  FIGS. 39 and 40 , conductive vias v that are extended from the conductive substrate  807  and are connected to the second conductivity type semiconductor layer  801  need to be provided. 
     The conductive vias v are internally connected to the second conductivity type semiconductor layer  801 . In order to reduce contact resistance, the number, shape, and pitch of the conductive vias v, and a contact area between the conductive vias v and the second conductivity type semiconductor layer  801  may be appropriately determined. Here, since the conductive vias v need to be electrically insulated from the active layer  802 , the first conductivity type semiconductor layer  803 , and the first conductive contact layer  804 , the insulator  806  is interposed therebetween. The insulator  806  may be formed of any substance having electrical insulation. However, since it is desirable to absorb the least amount of light, a silicon oxide or a silicon nitride, such as SiO 2 , SiO x N y , or Si x N y , may be used to form the insulator  806 . 
     As described above, in this embodiment, the conductive substrate  807  is connected to the second conductivity type semiconductor layer  801  through the conductive vias v, and there is no need to separately form an electrode on the upper surface of the second conductivity type semiconductor layer  801 . Therefore, the amount of light, emitted upward from the second conductivity type semiconductor layer  801 , may be increased. A light-emitting area will be reduced since the conductive vias v are formed in a portion of the active layer  802 . However, in spite of that, light extraction efficiency will be significantly improved since an electrode is removed from the upper surface of the second conductivity type semiconductor layer  801 . Meanwhile, it can be seen that the entire electrode arrangement of the second conductivity type semiconductor layer  801  according to this embodiment is similar to a horizontal electrode structure rather than a vertical electrode structure since an electrode is not disposed on the upper surface of the second conductivity type semiconductor layer  801 . However, sufficient current spreading effects can be ensured due to the conductive vias v formed inside the second conductivity type semiconductor layer  801 . 
     The high-resistance portion  808  is formed along the edge of the light-emitting structure, and protects the light-emitting structure, particularly, the active layer  802  against the outside environment, thereby increasing the electrical reliability of the device. Since the active layer  802 , exposed to the outside, may serve as a current leakage path, during the operation of the semiconductor light emitting device  800 , the high-resistance portion  808  with relatively high electrical resistance, is formed along the side of the light-emitting structure, thereby preventing a current leakage. Here, the high-resistance portion  808  may be formed by ion implantation. Specifically, when ions, accelerated by a particle accelerator, are implanted into the light-emitting structure, the crystals of the semiconductor layers forming the light-emitting structure are damaged to thereby increase resistance. Here, since the implanted ions can be restored by heat treatment, ions having a large particle size may be used so that the ions are not restored a general heat treatment temperature of semiconductor layers. For example, ions of atoms, such as Ar, C, N, Kr, Xe, Cr, O, Fe, and Ti, may be implanted into the light-emitting structure. 
       FIGS. 40 and 41  are cross-sectional views schematically illustrating modified embodiments of the semiconductor light emitting device of  FIG. 37 . First, a semiconductor light emitting device  800 - 1 , as shown in  FIG. 40 , is formed in such a manner that the sides of a light-emitting structure are inclined relative to the first conductive contact layer  804 . Specifically, the sides of the light-emitting structure are inclined toward the upper part of the light-emitting structure. As described below, the inclined light-emitting structure may be naturally obtained through a process of etching the light-emitting structure to expose the first conductive contact layer  804 . A semiconductor light emitting device  800 - 2 , as shown in  FIG. 41 , has unevenness formed on the upper surface of the light-emitting structure of the embodiment, described with reference to  FIG. 40 , and specifically, the upper surface of the second conductivity type semiconductor layer  801 . This unevenness may be appropriately provided using dry etching or wet etching. Here, an uneven structure having facets of irregular sizes, shapes, and periods may be provided by wet etching. This uneven structure may increase the possibility that light, made incident in a direction of the active layer  802 , is emitted to the outside. The modified embodiments, which have been described with reference to  FIGS. 40 and 41 , may be applied to other embodiments of  FIGS. 42 through 44 . 
       FIG. 42  is a cross-sectional view schematically illustrating a semiconductor light emitting device according to another exemplary embodiment of the invention. Referring to  FIG. 42 , like the above-described embodiment, in a semiconductor light emitting device  900  according to this embodiment, a first conductive contact layer  904  is formed on a conductive substrate  907 , and a light-emitting structure, that is, a first conductivity type semiconductor layer  903 , an active layer  902 , and a second conductivity type semiconductor layer  901  are provided on the first conductive contact layer  904 . A high-resistance portion  908  is formed on the edge of the light-emitting structure by ion implantation. The structural difference between this embodiment and the above-described embodiments is that the conductive substrate  907  is electrically connected to the first conductivity type semiconductor layer  903  rather than the second conductivity type semiconductor layer  901 . Therefore, the first conductive contact layer  904  is not necessarily required. Here, the first conductivity type semiconductor layer  903  and the conductive substrate  907  may come into direct contact with each other. 
     Conductive vias v, internally connected to the second conductivity type semiconductor layer  901 , pass through the active layer  902 , the first conductivity type semiconductor layer  903 , and the first conductive contact layer  904 , and are connected to the second conductive electrode  909 . The second conductive electrode  909  has an electrical connection portion that is extended from the conductive vias v toward the side of the light-emitting structure and is exposed to the outside. An electrode pad  905  may be formed on the electrical connection portion. Here, an insulator  906  is formed to electrically insulate the second conductive electrode  909  and the conductive vias v from the active layer  902 , the first conductivity type semiconductor layer  903 , the first conductive contact layer  904 , and the conductive substrate  907 . 
       FIG. 43  is a plan view schematically illustrating a semiconductor light emitting device according to another exemplary embodiment to the invention.  FIG. 44  is a schematic sectional view taken along the line B-B′ of the semiconductor light emitting device of  FIG. 43 . As described with reference to  FIGS. 37 through 39 , in a semiconductor light emitting device  800 ′ according to this embodiment, a first conductive contact layer  804 ′ is formed on a conductive substrate  807 ′, and a light-emitting structure, that is, a first conductivity type semiconductor layer  803 ′, an active layer  802 ′, and a second conductivity type semiconductor layer  801 ′ are formed on the first conductive contact layer  804 ′. A high-resistance portion  808 ′ is formed on the edge of the light-emitting structure by ion implantation. Furthermore, the first conductive contact layer  804 ′ is electrically insulated from the conductive substrate  807 ′. To this end, an insulator  806 ′ is interposed between the first conductive contact layer  804 ′ and the conductive substrate  807 ′. In this embodiment, the light-emitting structure is divided into a plurality of structures on the conductive substrate  807 ′. The light-emitting structure, divided into the plurality of structures, may increase light-scattering effects. Therefore, an improvement in the light extraction efficiency may be expected. In order to ensure a sufficient outside area, as shown in  FIG. 43 , the light-emitting structure may have a hexagonal shape. However, the invention is not limited thereto. Here, an increase in spacing between the divided structures of the light-emitting structure may reduce the area of the active layer  802 ′, which may cause a reduction in luminance efficiency. Therefore, the divided structures of the light-emitting structure may be brought into as close a contact as possible. As described above, when an etching process is performed in order to divide the light-emitting structure, the sides of the light-emitting structure need to be protected. A high-resistance portion  808 ′ may be formed on the sides of each of the divided structures of the light-emitting structure by ion implantation. 
     Hereinafter, a process of manufacturing the semiconductor light emitting device having the above-described configuration will be described. 
       FIGS. 45 through 53  are cross-sectional views illustrating the process flow of a method of manufacturing a semiconductor light emitting device according to this embodiment of the invention. Specifically, a method of manufacturing a semiconductor light emitting device having the configuration, having been described with reference to  FIGS. 37 to 39 , will be described. 
     First, as shown in  FIG. 45 , the second conductivity type semiconductor layer  801 , the active layer  802 , and the first conductivity type semiconductor layer  803  are sequentially grown on a semiconductor growth substrate B using a semiconductor layer growing process, such as MOCVD, MBE, or HVPE, thereby manufacturing a light-emitting structure. As for the semiconductor growth substrate B, a substrate, formed of SiC, MgAl 2 O 4 , MgO, LiAlO 2 , LiGaO 2 , or GaN may be used. Here, sapphire is a crystal having Hexa-Rhombo R3c symmetry (Hexa-Rhomho R3c) and has a lattice constant of 13.001 Å along the c-axis and a lattice constant of 4.758 Å along the a-axis. Orientation planes of the sapphire include the C(0001)plane, the A(1120)plane, and the R(1102)plane. Here, since nitride thin films are relatively easily grown on the C-plane sapphire substrate, which is stable at high temperatures, the C-plane sapphire substrate is widely used as a nitride growth substrate. 
     As shown in  FIG. 46 , the first conductive contact layer  804  is formed on the first conductivity type semiconductor layer  803 . The first conductive contact layer  804  may contain Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, or Au in consideration of light reflection function and ohmic contacts, formed together with first conductivity type semiconductor layer  803 , and may be formed using sputtering or deposition, both of which are known in the art. Then, as shown in  FIG. 47 , recesses are formed in the first conductive contact layer  804  and the light-emitting structure. Specifically, in subsequent operations, the recesses are filled with conductive materials to thereby form conductive vias connected to the second conductivity type semiconductor layer  801 . The recesses pass through the first conductive contact layer  804 , the first conductivity type semiconductor layer  803 , and the active layer  802 . The second conductivity type semiconductor layer  801  is exposed as the bottom surfaces of the recesses. The operation of forming recesses, shown in  FIG. 47 , may be performed using an etching process known in the related art, for example, ICP-RIE. 
     Then, as shown in  FIG. 48 , a material, such as SiO 2 , SiO x N y , or Si x N y , is deposited to form the insulator  806  so that the insulator  806  covers the top of the first conductive contact layer  804  and the side walls of the grooves. Here, since the second conductivity type semiconductor layer  801  corresponding to the bottom surfaces of the recesses needs to be at least partially exposed, the insulator  806  may be formed not to completely cover the bottom surfaces of the grooves. 
     Then, as shown in  FIG. 49 , conductive materials are formed within the recesses and on the insulator  806  to thereby form the conductive vias v and the conductive substrate  807 , so that the conductive substrate  807  is connected to the conductive vias v making contact with the second conductivity type semiconductor layer  801 . The conductive substrate  807  may include any one of the materials, such as Au, Ni, Al, Cu, W, Si, Se, and GaAs, by plating, sputtering, or deposition. Here, the conductive vias v and the conductive substrate  807  may be formed of the same material. Alternatively, when the conductive vias v and the conductive substrate  807  may be formed of different materials from each other, they may be formed using separate processes. For example, after the conductive vias v are formed by deposition, the conductive substrate  807  may be previously prepared and bonded to the light-emitting structure. 
     Then, as shown in  FIG. 50 , the semiconductor growth substrate B is removed to expose the second conductivity type semiconductor layer  801 . Here, the semiconductor growth substrate B may be removed using laser lift-off or chemical lift-off.  FIG. 50  is a view, rotated by 180 degrees, of  FIG. 49 , in which the semiconductor growth substrate B is removed. 
     Then, as shown in  FIG. 51 , the light-emitting structure, that is, the first conductivity type semiconductor layer  803 , the active layer  802 , and the second conductivity type semiconductor layer  801  are partially removed to expose the first conductive contact layer  804 , so that an electrical signal can be applied through the exposed first conductive contact layer  804 . Furthermore, as described above, the operation of removing the light-emitting structure may be used to divide the light-emitting structure into a plurality of structures. Though not shown in the drawing, an operation of forming an electrode pad on the exposed portion of the first conductive contact layer  804  may be further performed. In order to expose the first conductive contact layer  804 , the light-emitting structure may be etched using ICP-RIE or the like. Here, in order to prevent the material forming the first conductive contact layer  804  from moving to the side of the light-emitting structure and being attached thereto, as shown in  FIG. 52 , an etch-stop layer  809  may be previously formed inside the light-emitting structure. 
     Then, as shown in  FIG. 53 , the high-resistance portion  808  may be formed on the side surfaces of the light-emitting structure. The high-resistance portion  808  corresponds to a region where crystals of the semiconductor layer forming the light-emitting structure are damaged by ions implanted to the side thereof. Here, since the implanted ions may be restored by heat treatment, ions having a large particle size may be used so that the ions are not restored a general heat treatment temperature of the semiconductor layer. For example, ions of atoms, such as Ar, C, N, Kr, Xe, Cr, O, Fe, and Ti, may be implanted into the light-emitting structure. 
       FIGS. 54 through 57  are cross-sectional views illustrating the process flow of a method of manufacturing a semiconductor light emitting device according to another exemplary embodiment of the invention, and specifically, a method of manufacturing the semiconductor light emitting device, as shown in  FIG. 42 . Here, the operations, having been described with  FIGS. 45 through 47 , may be directly applied to this embodiment. Hereinafter, subsequent operations to the operation of forming recesses in the first conductive contact layer  904  and the light-emitting structure will be described. 
     First, as shown in  FIG. 54 , a material, such as SiO 2 , SiO x N y , or Si x N y , is deposited to form the insulator  906  in order to cover the upper part of the first conductive contact layer  904  and the side walls of the recesses. Here, the insulator  906  may be referred to as a first insulator to differentiate the first insulator from an insulator to be formed to cover the second conductive electrode  909  in subsequent operations. Unlike the above-described embodiments, the insulator  906  is not formed on the entire upper surface of the first conductive contact layer  904  in this embodiment, so that the conductive substrate  907  and the first conductive contact layer  904  come into contact with each other. That is, the insulator  906  may be formed in consideration of a portion of the upper surface of the first conductive contact layer  904 , and specifically, a region where the second conductive electrode  909 , connected to the second conductivity type semiconductor layer  901 , is formed. 
     Then, as shown in  FIG. 55 , conductive materials are formed within the recesses and on the insulator  906  to thereby form the second conductive electrode  909 , so that the second conductive electrode  909  includes the conductive vias v connected to the second conductivity type semiconductor layer  901 . In this operation, the insulator  906  is previously formed at a position where the second conductive electrode  909  will be formed, thereby forming the second conductive electrode  909  according to the insulator  960 . In particular, the second conductive electrode  909  may be exposed to the outside and be extended in a horizontal direction from the conductive vias v so as to serve as an electrical connection portion. 
     Then, as shown in  FIG. 56 , the insulator  906  is formed to cover the second conductive electrode  909 , and the conductive substrate  907  is formed thereon so as to be electrically connected to the first conductive contact layer  904 . Here, the insulator  906 , formed in this operation, may be referred to as a second insulator. The earlier insulator and this insulator  906  may form a single insulating structure. In this operation, the second conductive electrode  909  may be electrically insulated from the first conductive contact layer  904  and the conductive substrate  907 . Then, as shown in  FIG. 57 , the second conductivity type semiconductor layer  901  is removed to expose the semiconductor growth substrate B. Though not shown in the drawings, an operation of partially removing the light-emitting structure to expose the second conductive electrode  909  and an operation of forming the high-resistance portion  908  on the side surfaces of the light-emitting structure by ion implantation may be performed using the above-described operations. 
     A semiconductor light emitting device will according to another exemplary embodiment of the invention will be described with reference to  FIGS. 58 through 77 . 
       FIG. 58  is a perspective view schematically illustrating a semiconductor light emitting device according to this embodiment.  FIG. 59  is a schematic plan view illustrating a second conductivity type semiconductor layer of the semiconductor light emitting device as viewed from top of  FIG. 58 .  FIG. 60  is a schematic sectional view taken along the line A-A′, of  FIG. 59 , of the semiconductor light emitting device of  FIG. 58 . In a semiconductor light emitting device  1000  according to this embodiment, a first conductive contact layer  1004  is formed on a conductive substrate  1007 , and a light-emitting structure, that is, a first conductivity type semiconductor layer  1003 , an active layer  1002 , and a first conductivity type semiconductor layer  1001 , are formed on the first conductive contact layer  1004 . An undoped semiconductor layer  1008  is formed on the first conductivity type semiconductor layer  1001 . Unevenness is provided on the upper surface of the undoped semiconductor layer  1008 , thereby increasing the external extraction efficiency of light emitted from the active layer  1002 . The first conductive contact layer  1004  is electrically insulated from the conductive substrate  1007 . To this end, an insulator  1006  is interposed between the first conductive contact layer  1004  and the conductive substrate  1007 . 
     In this embodiment, the first and second conductivity type semiconductor layers  1003  and  1001  may be p-type and n-type semiconductor layers, respectively, and may be formed of nitride semiconductors. Therefore, in this embodiment, first conductive and second conductive may mean p-type and n-type, respectively. However, the invention is not limited thereto. The first and second conductivity type semiconductor layers  1003  and  1001  may satisfy an equation of Al x In y Ga (1-x-y) N (where 0≤x≤1, 0≤y≤1, and 0≤x+y≤1 are satisfied), for example, GaN, AlGaN, and InGaN. The active layer  1002 , formed between the first and conductive semiconductor layers  1003  and  1001 , emits light having a predetermined amount of energy by electron-hole recombination and may have a multiple quantum well (MQW) structure in which quantum well layers and quantum barrier layers alternate with each other. As for the multiple quantum well structure, an InGaN/GaN structure may be used. 
     The first conductive contact layer  1004  may reflect light, emitted from the active layer  1002 , upward from the semiconductor light emitting device  1000 , that is, toward the second conductivity type semiconductor layer  1001 . Further, the first conductive contact layer  1004  and the first conductivity type semiconductor layer  1003  may form ohmic contacts. In consideration of these functions, the first conductive contact layer  1004  may contain Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, or Au. Here, though not illustrated in detail, the first conductive contact layer  1004  may have a dual or multi-layered structure to thereby increase reflection efficiency. For example, the first conductive contact layer  1004  may have a structure of Ni/Ag, Zn/Ag, Ni/Al, Zn/Al, Pd/Ag, Pd/Al, Ir/Ag, Ir/Au, Pt/Ag, Pt/Al, or Ni/Ag/Pt. In this embodiment, a portion of the first conductive contact layer  1004  may be exposed to the outside. As shown in the drawings, the light-emitting structure may not be formed on the exposed portion. The exposed portion of the first conductive contact layer  1004  corresponds to an electrical connection portion to which an electrical signal is applied. An electrode pad  1005  may be formed on the exposed portion thereof. 
     As described below, the conductive substrate  1007  serves as a support that holds the light-emitting structure during a laser-lift off process and may be formed of a material containing any one of Au, Ni, Al, Cu, W, Si, Se, and GaAs, for example, Si—Al alloys. Here, according to the selected material, the conductive substrate  1007  may be formed using plating or bonding. In this embodiment, the conductive substrate  1007  is electrically connected to the second conductivity type semiconductor layer  1001 , so that an electrical signal may be applied to the second conductivity type semiconductor layer  1001  through the conductive substrate  1007 . To this end, as shown in  FIGS. 59 and 60 , conductive vias v that are extended from the conductive substrate  1007  and are connected to the second conductivity type semiconductor layer  1001  need to be provided. 
     The conductive vias v are internally connected to the second conductivity type semiconductor layer  1001 . In order to reduce contact resistance, the number, shape, and pitch of the conductive vias v, and a contact area between the conductive vias v and the second conductivity type semiconductor layer  1001  may be appropriately determined. Here, since the conductive vias v need to be electrically insulated from the active layer  1002 , the first conductivity type semiconductor layer  1003 , and the first conductive contact layer  1004 , the insulator  1006  is interposed therebetween. The insulator  1006  may be formed of any substance having electrical insulation. However, since it is desirable to absorb the least amount of light, a silicon oxide or a silicon nitride, such as SiO 2 , SiO x N y , or Si x N y , may be used to form the insulator  1006 . 
     As described above, in this embodiment, the conductive substrate  1007  is connected to the second conductivity type semiconductor layer  1001  through the conductive vias v, and there is no need to separately form an electrode on the upper surface of the second conductivity type semiconductor layer  1001 . Therefore, the amount of light, emitted upward from the second conductivity type semiconductor layer  1001 , may be increased. A light-emitting area will be reduced since the conductive vias v are formed in a portion of the active layer  1002 . However, in spite of that, light extraction efficiency will be significantly improved since an electrode is removed from the upper surface of the second conductivity type semiconductor layer  1001 . Meanwhile, it can be seen that the entire electrode arrangement of the second conductivity type semiconductor layer  1001 , according to this embodiment, is similar to a horizontal electrode structure rather than a vertical electrode structure, since an electrode is not disposed on the upper surface of the second conductivity type semiconductor layer  1001 . However, sufficient current spreading effects can be ensured due to the conductive vias v formed inside the second conductivity type semiconductor layer  1001 . 
     The undoped semiconductor layer  1008  is formed on the upper surface of the second conductivity type semiconductor layer  1001 . As described below, the undoped semiconductor layer  1008  is employed as a buffer layer before the growth of the semiconductor layers forming the light-emitting structure. Here, “undoped” means a state in which a semiconductor layer does not undergo a separate impurity-doping process. When a semiconductor layer having a predetermined level of impurity concentration, for example, if a gallium nitride having a concentration of is grown using MOCVD, Si having a concentration of approximately 10 16  to 10 18 /cm 3 , being used as a dopant, may be contained without intention. In this embodiment, since an electrode does not have to be formed on the upper surface of the second conductivity type semiconductor layer  1001 , the undoped semiconductor layer  1008  is not removed. Therefore, the undoped semiconductor layer  1008  may be formed to cover the entire upper surface of the second conductivity type semiconductor layer  1001 . Further, an uneven structure is formed on the undoped semiconductor layer  1008 , thereby increasing the possibility that light, made incident in the direction of the active layer  1002 , is emitted to the outside. In this embodiment, the description has been made to a case in which unevenness is only applied to the undoped semiconductor layer  1008 . However, depending on etching conditions, unevenness may further be formed on a portion of the second conductivity type semiconductor layer  1001 . 
     When the undoped semiconductor layer  1008  is removed, and an uneven structure is then formed on the second conductivity type semiconductor layer  1001 , a part of the second conductivity type semiconductor layer  1001  may be damaged. In particular, if an unevenness forming process is not accurately controlled, the uniform thickness of the second conductivity type semiconductor layer  1001  may not be maintained, depending on products. Therefore, like this embodiment, the electrode connection structure of the second conductivity type semiconductor layer  1001  is formed at the lower part thereof through the inside of the second conductivity type semiconductor layer  1001 , these problems may be solved by forming the uneven structure on the undoped semiconductor layer  1008  not being removed. 
       FIGS. 61 and 62  are cross-sectional views schematically illustrating a modified embodiment of the semiconductor light emitting device of  FIG. 58 . First, a light emitting device  1000 - 1 , as shown in  FIG. 61 , is formed in such a manner that the side surfaces of a light-emitting structure are inclined relative to the first conductive contact layer  1004 . Specifically, the side surfaces of the light-emitting structure are inclined toward the upper part of the light-emitting structure. As described below, the inclined light-emitting structure may be naturally obtained through a process of etching the light-emitting structure to expose the first conductive contact layer  1004 . A semiconductor light emitting device  1000 - 2 , as shown in  FIG. 61 , further includes a passivation layer  1009  in order to cover the side surfaces of the light-emitting structure of  FIG. 61 . The passivation layer  1009  protects the light-emitting structure, and particularly, the active layer  1002  against the outside environment. The passivation layer  1009  may be formed of a silicon oxide or a silicon nitride, such as SiO 2 , SiO x N y , or Si x N y , and may have a thickness of approximately 0.1 to 2 μm. 
     Since the active layer  1002 , exposed to the outside, may serve as a current leakage path, during the operation of the semiconductor light emitting device  1000 , this problem can be prevented by forming the passivation layer  1009  on the side surfaces of the light-emitting structure. Considering this aspect, as shown in  FIG. 62 , the passivation layer  1009  may further be extended to the exposed upper surface of the first conductive contact layer  1004 . The modified embodiments, having been described with reference to  FIGS. 61 and 62 , may be applied to other embodiments of  FIGS. 63 and 64 . 
       FIG. 63  is a cross-sectional view schematically illustrating a semiconductor light emitting device according to another exemplary embodiment of the invention. Referring to  FIG. 63 , like the above-described embodiment, in a semiconductor light emitting device  1100  according to this embodiment, a first conductive contact layer  1104  is formed on a conductive substrate  1107 , and a light-emitting structure, that is, a first conductivity type semiconductor layer  1103 , an active layer  1102 , and a second conductivity type semiconductor layer  1101  are formed on the first conductive contact layer  1104 . An undoped semiconductor layer  1108  is formed on the first conductivity type semiconductor layer  1101 . Unevenness is provided on the upper surface of the undoped semiconductor layer  1108 . The first conductive contact layer  1104  is electrically insulated from the conductive substrate  1107 . To this end, an insulator  1106  is interposed between the first conductive contact layer  1104  and the conductive substrate  1107 . 
     Unlike the above-described embodiments, in which the electrical connection portion of the first conductive contact layer  1104  is formed at a position corresponding to the edge of the light-emitting structure as viewed from the top of the light-emitting structure, in this embodiment, the electrical connection portion of the first conductive contact layer  1104  is formed at a position corresponding to the center of the light-emitting structure as viewed from the top of the light-emitting structure. As such, the position of the exposed region of the first conductive contact layer  1104  may be changed upon necessity in this invention. An electrode pad  1105  may be formed on the electrical connection portion of the first conductive contact layer  1104 . 
       FIG. 64  is a cross-sectional view schematically illustrating a semiconductor light emitting device according to another exemplary embodiment of the invention. Referring to  FIG. 64 , in a semiconductor light emitting device  1200  according to this embodiment, a first conductive contact layer  1204  is formed on a conductive substrate  1207 , and a light-emitting structure, that is, a first conductivity type semiconductor layer  1203 , an active layer  1202 , and a second conductivity type semiconductor layer  1201  are formed on the first conductive contact layer  1204 . An undoped semiconductor layer  1208  is formed on the light emitting structure, that is, on the first conductivity type semiconductor layer  1201 . An uneven structure is formed on the upper surface of the undoped semiconductor layer  1208 . The structural difference between the semiconductor light emitting device  1200  according to this embodiment and the above-described embodiments is that the conductive substrate  1207  is electrically connected to the first conductivity type semiconductor layer  1203  rather than the second conductivity type semiconductor layer  1201 . Therefore, the first conductive contact layer  1204  is not necessarily required. In this case, the first conductivity type semiconductor layer  1203  may come into direct contact with the conductive substrate  1207 . 
     Conductive vias v, which are internally connected to the second conductivity type semiconductor layer  1201 , pass through the active layer  1202 , the first conductivity type semiconductor layer  1203 , and the first conductive contact layer  1204 , and are connected to the second conductive electrode  1209 . The second conductive electrode  1209  has an electrical connection portion that is extended from the conductive vias v toward the side of the light-emitting structure and is exposed to the outside. An electrode pad  1205  may be formed on the electrical connection portion. Here, an insulator  1206  is formed to electrically insulate the second conductive electrode  1209  and the conductive vias v from the active layer  1202 , the first conductivity type semiconductor layer  1203 , the first conductive contact layer  1204 , and the conductive substrate  1207 . 
     Hereinafter, a process of manufacturing the semiconductor light emitting device having the above-described configuration will be described. 
       FIGS. 65 through 73  are cross-sectional views illustrating the process flow of a method of manufacturing a semiconductor light emitting device according to this embodiment of the invention. Specifically, a method of manufacturing a semiconductor light emitting device having the configuration, having been described with reference to  FIGS. 58 to 60 , will be described. 
     First, as shown in  FIG. 65 , the second conductivity type semiconductor layer  1001 , the active layer  1002 , and the first conductivity type semiconductor layer  1003  are sequentially grown on a semiconductor growth substrate B using a semiconductor layer growing process, such as MOCVD, MBE, or HVPE, thereby manufacturing a light-emitting structure. Here, as described above, in terms of configuration, the light-emitting structure is defined as a configuration having the second conductivity type semiconductor layer  1001 , the active layer  1002 , and the first conductivity type semiconductor layer  1003 , while in terms of growth and etching, the buffer layer  1008  can be considered a component forming the light-emitting structure. Therefore, hereinafter, the light-emitting structure will be defined as a configuration having the buffer layer  1008 , the second conductivity type semiconductor layer  1001 , the active layer  1002 , and the first conductivity type semiconductor layer  1003 . 
     As for the semiconductor growth substrate B, a substrate, formed of SiC, MgAl 2 O 4 , MgO, LiAlO 2 , LiGaO 2 , or GaN may be used. Here, sapphire is a crystal having Hexa-Rhombo R3c symmetry (Hexa-Rhombo R3c) and has a lattice constant of 13.001 Å along the c-axis and a lattice constant of 4.758 Å along the a-axis. Orientation planes of the sapphire include the C(0001)plane, the A(1120)plane, and the R(1102)plane. Here, since nitride thin films are relatively easily grown on the C-plane sapphire substrate, which is stable at high temperatures, the C-plane sapphire substrate is widely used as a nitride growth substrate. As described above, as for the buffer layer  1008 , an undoped semiconductor layer, formed of a nitride, may be used to prevent the lattice defects of the light-emitting structure to be formed thereon. 
     Then, as shown in  FIG. 66 , the first conductive contact layer  1004  is formed on the first conductivity type semiconductor layer  1003 . The first conductive contact layer  1004  may contain Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, or Au in consideration of light reflection function and ohmic contacts, formed together with first conductivity type semiconductor layer  1003 , and may be formed using sputtering or deposition, which both of which are known in the art. Then, as shown in  FIG. 67 , recesses are formed in the first conductive contact layer  1004  and the light-emitting structure. Specifically, in subsequent operations, the recesses are filled with conductive materials to thereby form conductive vias connected to the second conductivity type semiconductor layer  1001 . The recesses pass through the first conductive contact layer  1004 , the first conductivity type semiconductor layer  1003 , and the active layer  1002 . The second conductivity type semiconductor layer  1001  is exposed as the bottom surface of the recesses. The operation of forming recesses, shown in  FIG. 67 , may be performed using an etching process known in the related art, for example, ICP-RIE. 
     Then, as shown in  FIG. 68 , a material, such as SiO 2 , SiO x N y , or Si x N y , is deposited to form the insulator  1006  so that the insulator  1006  covers the top of the first conductive contact layer  1004  and the side walls of the grooves. Here, since the second conductivity type semiconductor layer  1001  corresponding to the bottom surfaces of the recesses needs to be at least partially exposed, the insulator  1006  may be formed so as not to completely cover the bottom surfaces of the grooves. 
     Then, as shown in  FIG. 69 , conductive materials are formed within the recesses and on the insulator  1006  to thereby form the conductive vias v and the conductive substrate  1007 , so that the conductive substrate  1007  is connected to the conductive vias v making contact with the second conductivity type semiconductor layer  1001 . The conductive substrate  1007  may include any one of the materials, such as Au, Ni, Al, Cu, W, Si, Se, and GaAs, by any one of plating, sputtering, and deposition. Here, the conductive vias v and the conductive substrate  1007  may be formed of the same material. Alternatively, when the conductive vias v and the conductive substrate  1007  may be formed of different materials from each other, they may be formed using separate processes. For example, after the conductive vias v are formed by deposition, the conductive substrate  1007  may be previously prepared and bonded to the light-emitting structure. 
     As shown in  FIG. 70 , the semiconductor growth substrate B is removed to expose the buffer layer  1008 . Here, the semiconductor growth substrate B may be removed using laser lift-off or chemical lift-off.  FIG. 70  is a view, rotated by 180 degrees, of  FIG. 68 , in which the semiconductor growth substrate B is removed. 
     Then, as shown in  FIG. 71 , the light-emitting structure, that is, the buffer layer  1008 , the first conductivity type semiconductor layer  1003 , the active layer  1002 , and the second conductivity type semiconductor layer  1001  are partially removed to expose the first conductive contact layer  1004 , so that an electrical signal can be applied through the exposed first conductive contact layer  1004 . Though not shown in the drawings, an operation of forming an electrode pad on the exposed portion of the first conductive contact layer  1004  may be further performed. In order to expose the first conductive contact layer  1004 , the light-emitting structure may be etched using ICP-RIE or the like. Here, in order to prevent the material, forming the first conductive contact layer  1004 , from moving to the side of the light-emitting structure and being attached thereto, as shown in  FIG. 72 , an etch-stop layer  1010  may be previously formed inside the light-emitting structure. Furthermore, as a more reliable insulating structure, after etching the light-emitting structure, the passivation layer  1009 , as shown in  FIG. 62 , may be formed on the side surfaces of the light-emitting structure. 
     Then, as shown in  FIG. 73 , an uneven structure is formed on the buffer layer  1008 . Here, unevenness may be mainly formed on the upper surface of the buffer layer  1008  that is exposed by removing the semiconductor growth substrate B. This uneven structure may increase light extraction efficiency. Here, the uneven structure may be formed using dry or wet etching. Here, an uneven structure having facets of irregular sizes, shapes, and periods may be provided by wet etching. In this embodiment, an electrical signal is smoothly applied to the first conductivity type semiconductor layer  1001  without removing the buffer layer  1008  with low electrical conductivity. By forming the uneven structure on the buffer layer  1008 , the uniform thickness of the first conductivity type semiconductor layer  1001  can be ensured. 
       FIGS. 74 through 77  are cross-sectional views illustrating the process flow of a method of manufacturing a semiconductor light emitting device according to another exemplary embodiment of the invention. Specifically, a method of manufacturing the semiconductor light emitting device having the configuration, having been described with reference to  FIG. 64 , will be described. The operations, having been described with reference to  FIGS. 65 through 67 , may be directly applied to this embodiment. Hereinafter, operations subsequent to the operation of forming the recesses in the first conductive contact layer  1204  and the light-emitting structure will be described. 
     First, as shown in  FIG. 74 , a material, such as SiO 2 , SiO x N y , or Si x N y , is deposited to form the insulator  1206  in order to cover the upper part of the first conductive contact layer  1204  and the side walls of the recesses. Here, the insulator  1206  may be referred to as a first insulator to differentiate the first insulator from an insulator to be formed to cover the second conductive electrode  1209  in subsequent operations. Unlike the above-described embodiments, the insulator  1206  is not formed on the entire upper surface of the first conductive contact layer  1204  in this embodiment, so that the conductive substrate  1207  and the first conductive contact layer  1204  come into contact with each other. That is, the insulator  1206  may be formed in consideration of a portion of the upper surface of the first conductive contact layer  1204 , and specifically, a region in which the second conductive electrode  1209 , connected to the second conductivity type semiconductor layer  1201 , is formed. 
     Then, as shown in  FIG. 75 , conductive materials are formed within the recesses and on the insulator  1206  to thereby form the second conductive electrode  1209 , so that the second conductive electrode  1209  includes the conductive vias v connected to the second conductivity type semiconductor layer  1201 . In this operation, the insulator  1206  is previously formed at a position where the second conductive electrode  1209  will be formed, thereby forming the second conductive electrode  1209  according to the insulator  1206 . In particular, the second conductive electrode  1209  is exposed to the outside and is extended in a horizontal direction from the conductive vias v so as to serve as an electrical connection portion. 
     Then, as shown in  FIG. 76 , the insulator  1206  is formed to cover the second conductive electrode  1209 , and the conductive substrate  1207  is formed thereon so as to be electrically connected to the first conductive contact layer  1204 . Here, the insulator  1206 , formed in this operation, may be referred to as a second insulator. The earlier insulator and the insulator  1206  may form a single insulating structure. In this operation, the second conductive electrode  1209  may be electrically insulated from the first conductive contact layer  1204  and the conductive substrate  1207 . Then, as shown in  FIG. 77 , the second conductivity type semiconductor layer  1201  is removed to expose the semiconductor growth substrate B. Though not shown in the drawings, an operation of partially removing the light-emitting structure to expose the second conductive electrode  1209  and an operation of forming the high-resistance portion  1208  along the side surfaces of the light-emitting structure by ion implantation may be then performed using the above-described operations. 
     A semiconductor light emitting device according to another exemplary embodiment of the invention will now be described with reference to  FIGS. 78 through 91 . 
       FIG. 78  is a cross-sectional view schematically illustrating a semiconductor light emitting device according to this embodiment.  FIG. 79A  and  FIG. 79  B are circuit diagrams illustrating the semiconductor light emitting device of  FIG. 78 . Referring to  FIG. 78 , in a semiconductor light emitting device  1300  according to this embodiment, a plurality of light-emitting structures C 1  and C 2  are formed on a substrate  1306  while the light-emitting structures C 1  and C 2  are electrically connected to each other. Here, two light-emitting structures are referred to as first and second light-emitting structures C 1  and C 2 , respectively. The first and second light-emitting structures C 1  and C 2  each have a first conductivity type semiconductor layer  1303 , an active layer  1302 , and a second conductivity type semiconductor layer  1301  stacked upon each other in a sequential manner on the substrate  1306 , and have first and second electrical connection portions  1304  and  1307 , respectively, in order to provide an electrical connection therebetween. 
     The first electrical connection portion  1304  is formed under the first conductivity type semiconductor layer  1303 , and may provide ohmic contacts and light reflection function in addition to electrical connections. The second electrical connection portion  1307  may be electrically connected to the second conductivity type semiconductor layer  1301  and have conductive vias v passing through the first electrical connection portion  1304 , the first conductivity type semiconductor layer  1303 , and the active layer  1302  so as to be connected to the second conductivity type semiconductor layer  1301 . The second connection portion of the first light-emitting structure C 1 , that is, the conductive vias v and the first electrical connection portion  1304  of the second light-emitting structure C 2  are electrically connected to each other through the substrate  1306 . To this end, the substrate  1306  is formed of a material having electrical conductivity. As the substrate  1306  has this electrical connection structure, the semiconductor light emitting device  1300  can be operated even though external AC power is applied. 
     In this embodiment, the first and second conductivity type semiconductor layers  1303  and  1301  may be p-type and n-type semiconductor layers, respectively, and may be formed of nitride semiconductors. Therefore, in this embodiment, first conductive and second conductive may mean p-type and n-type, respectively. The invention is not limited thereto, however. The first and second conductivity type semiconductor layers  1303  and  1301  may satisfy an equation of Al x In y Ga (1-x-y) N (where 0≤x≤1, 0≤y≤1, and 0≤x+y≤1 are satisfied), for example, GaN, AlGaN, and InGaN. The active layer  1302 , formed between the first and conductive semiconductor layers  1303  and  1301 , emits light having a predetermined amount of energy by electron-hole recombination and may have a multiple quantum well (MQW) structure in which quantum well layers and quantum barrier layers alternate with each other. As for the multiple quantum well structure, an InGaN/GaN structure may be used. 
     As described above, the first conductive contact layer  1304  may reflect light, emitted from the active layer  1302 , upward from the semiconductor light emitting device  1300 , that is, toward the second conductivity type semiconductor layer  1301 . Further, the first conductive contact layer  1304  and the first conductivity type semiconductor layer  1303  may form ohmic contacts. In consideration of these functions, the first conductive contact layer  1304  may contain Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, or Au. Here, though not illustrated in detail, the first conductive contact layer  1304  may have a dual or multi-layered structure to thereby increase reflection efficiency. For example, the first conductive contact layer  1304  may have a structure of Ni/Ag, Zn/Ag, Ni/Al, Zn/Al, Pd/Ag, Pd/Al, Ir/Ag, Ir/Au, Pt/Ag, Pt/Al, or Ni/Ag/Pt. 
     When manufacturing the semiconductor light emitting device  1300 , the substrate  1306  serves as a support that holds the first and second light-emitting structures C 1  and C 2  during a laser-lift off process. In order to electrically connect the first and second light-emitting structures C 1  and C 2  to each other, a conductive substrate may be used. The substrate  1306  may be formed of a conductive material containing any one of Au, Ni, Al, Cu, W, Si, Se, and GaAs, for example, Si—Al alloys. Here, according to the selected material, the substrate  1306  may be formed by plating or bonding. 
     The conductive vias v, provided in the second electrical connection portion  1307 , are internally connected to the second conductivity type semiconductor layer  1301 . In order to reduce contact resistance, the number, shape, and pitch of the conductive vias v, and a contact area between the conductive vias v and the second conductivity type semiconductor layer  1301  may be appropriately controlled. Here, since the conductive vias v need to be electrically insulated from the active layer  1302 , the first conductivity type semiconductor layer  1303 , and the first conductive contact layer  1304 , the insulator  1305  is interposed therebetween. The insulator  1305  may be formed of any substance having electrical insulation. However, since it is desirable to absorb the least amount of light, a silicon oxide or a silicon nitride, such as SiO 2 , SiO x N y , or Si x N y , may be used to form the insulator  1305 . 
     Like this embodiment, the second conductivity type semiconductor layer  1301  is formed through the second electrical connection portion  1307  at a lower portion thereof, there is no need to separately form an electrode on the upper surface of the second conductivity type semiconductor layer  1301 . Therefore, the amount of light, emitted upward from the second conductivity type semiconductor layer  1301 , may be increased. A light-emitting area will be reduced since the conductive vias v are formed in a portion of the active layer  1302 . However, in spite of that, light extraction efficiency will be significantly improved since there is no need to form an electrode on the upper surface of the second conductivity type semiconductor layer  1301 . Meanwhile, it can be seen that the entire electrode arrangement of the second conductivity type semiconductor layer  1301 , according to this embodiment, is similar to a horizontal electrode structure, rather than a vertical electrode structure, since an electrode is not disposed on the upper surface of the second conductivity type semiconductor layer  1301 . However, sufficient current spreading effects can be ensured due to the conductive vias v formed inside the second conductivity type semiconductor layer  1301 . Furthermore, an uneven structure may be formed on the upper surface of the second conductivity type semiconductor layer  1301  to thereby increase the possibility that light incident in a direction of the active layer  1302  is emitted to the outside. 
     As described above, the semiconductor light emitting device  1300  may be driven by AC power. To this end, as shown in  FIGS. 79A and 79B , the first and second light-emitting structures C 1  and C 2  form an n-p junction. This n-p junction may be formed in such a manner that the second electrical connection portion v of the first light-emitting structure C 1  and the first electrical connection portion  1304  of the second light-emitting structure C 2  are connected to each other, external power is applied to the first electrical connection portion  1304  of the light-emitting structure C 1  and the second electrical connection portion  1307  of the second light-emitting structure C 2 . Specifically, in  FIG. 79A , terminals A and B correspond to the first electrical connection portion  1304  of the first light-emitting structure C 1  and the second electrical connection portion  1307  of the second light-emitting structure C 2 , respectively. A terminal C corresponds to the substrate  1306 . Here, as shown in  FIG. 79B , when the terminals A and B are connected to each other, and an AC signal is applied to the terminals A and B connected to each other and the terminal C, an AC light emitting device may be realized. 
       FIGS. 80 through 82  are cross-sectional views schematically illustrating modified embodiments of the semiconductor light emitting device of  FIG. 78 . An electrical connection structure between light-emitting structures of the semiconductor light emitting device according to the modified embodiment, as shown in  FIGS. 80 through 82 , is different from that of the above-described embodiment. A circuit diagram of the realized semiconductor light emitting device is the same as that of  FIG. 80 . First, in a semiconductor light emitting device  1400 , first and second light-emitting structures C and C 2  are disposed on a substrate  1406 . Here, the first light-emitting structure C 1  has the same configuration as the first light-emitting structure of  FIG. 78 . Unlike the above-described embodiment, a vertical electrode structure can be used as a part of the light-emitting structure. Specifically, the second light-emitting structure C 2  corresponds to a vertical electrode structure. Specifically, a first conductivity type semiconductor layer  1403 , an active layer  1402 , and a second conductivity type semiconductor layer  1401  may be sequentially formed on the first electrical connection portion  1404  connected to the substrate  1406 . A second electrical connection portion  1407  is formed on the second conductivity type semiconductor  1401 . 
     Then, the embodiments of  FIGS. 81 and 82  have configurations in which the substrates are formed of electrically insulating materials as shown in  FIGS. 78 and 79 , respectively. In a semiconductor light emitting device  1500 , as shown in  FIG. 81 , first and second light-emitting structures C 1  and C 2  are disposed on a substrate  1506  having electrical insulation. Here, like the embodiment of  FIG. 78 , the first and second light-emitting structures C 1  and C 2  each have a first conductivity type semiconductor layer  1503 , an active layer  1502 , and a second conductivity type semiconductor layer  1501  stacked upon each other in a sequential manner on a substrate  1506 . Second electrical connection portions  1507   a  and  1507   b  have conductive vias v connected to the second conductivity type semiconductor layer  1501 . Furthermore, an insulator  1505  is formed in order that the second electrical connection portions  1507   a  and  1507   b  are electrically insulated from the first electrical connection portion  1504 , the first conductivity type semiconductor layer  1503 , and the active layer  1502 . As the substrate  1506  having electrical insulation is used, the second electrical connection portion  1507   a  of the first light-emitting structure C 1  is connected to the first electrical connection portion  1504  of the second light-emitting structure C 2  by portions extended in parallel with the substrate  1506  from the conductive vias v. 
     In a similar manner, like the embodiment of  FIG. 80 , in a semiconductor light emitting device  1600 , as shown in  FIG. 82 , a second light-emitting structure C 2  has a first conductivity type semiconductor layer  1603 , an active layer  1602 , and a second conductivity type semiconductor layer  1601  formed on a first electrical connection portion  1604  in a sequential manner. A second electrical connection portion  1607  is formed on the second conductivity type semiconductor  1601 . As the substrate  1606  having electrical insulation is used, a second electrical connection portion  1607   a  of a first light-emitting structure C 1  is extended in parallel with the substrate  1606  to the second light-emitting structure C 2  from conductive vias v connected to the second conductivity type semiconductor layer  1601 . Therefore, the first and second light-emitting structures C 1  and C 2  may share the second electrical connection portion  1607   a.    
     Meanwhile, as for the above-described embodiments, an AC driven light emitting device is realized using two light-emitting structures. However, the light-emitting structure, that is, the number of light emitting diodes and a connection structure thereof may vary.  FIG. 83  is a circuit diagram illustrating the semiconductor light emitting device according to this embodiment. In  FIG. 83 , one diode is a light emitting diode and corresponds to a light-emitting structure. The circuit diagram, shown in  FIG. 83 , is a so-called ladder network circuit and has fourteen light-emitting structures. In this embodiment, when a forward voltage is applied, nine light-emitting structures are operated. Even when a reverse voltage is applied, nine light-emitting structures are operated. To this end, there are provided three basic electrical connection structures. As shown in  FIG. 83 , these three electrical connection structures are an n-p junction, an n-n junction, and a p-p junction. Examples of the n-p junction, the n-n junction, and the p-p junction will be described below. By using these basic junctions, an AC driven light emitting device having many different numbers of light emitting diodes and circuit configurations can be obtained. 
     First,  FIGS. 84 and 85  are cross-sectional views schematically illustrating an example of an n-p junction. Referring to  FIGS. 84 and 85 , the first and second light-emitting structures C 1  and C 2  forming an n-p junction are disposed on substrates  1706  and  1706 ′. The first and second light-emitting structures C 1  and C 2  have a first conductivity type semiconductor layer  1703 , an active layer  1702 , and a second conductivity type semiconductor layer  1701  sequentially stacked on a first electrical connection portion  1704 . An insulator  1705  is formed in order to electrically insulate conductive vias v, internally connected to the second conductivity type semiconductor layer  1701 , from the first electrical connection portion  1704 , the first conductivity type semiconductor layer  1703 , and the active layer  1702 . A second electrical connection portion  1707  of the first light-emitting structure C 1  is connected to the first electrical connection portion  1704  of the second light-emitting structure C 2 . Here, the configuration of  FIG. 84 , using the conductive substrate  1706 , and the configuration of  FIG. 85 , using the electrical insulating substrate  1706 ′, create slightly different shapes of the second electrical connection portion  1707 , which are similar to the configurations of  FIGS. 78 and 81 , respectively. However, since in order to implement AC driving, the n-p junction is connected to another light-emitting structure to form the entire device, rather than being solely used, the second electrical connection portion provided in the second light-emitting structure C 2 , that is, the conductive vias v may be electrically connected to another light-emitting structure rather than a structure for applying an external electrical signal. 
     Then,  FIGS. 86 through 88  are cross-sectional views schematically illustrating an example of an n-n junction. Referring to  FIGS. 86 through 88 , first and second light-emitting structures C 1  and C 2  forming an n-n junction are disposed on substrates  1806  and  1806 ′. The first and second light-emitting structures C 1  and C 2  each have a configuration in which a first conductivity type semiconductor layer  1803 , an active layer  1802 , and a second conductivity type semiconductor layer  1801  are sequentially stacked on a first electrical connection portion  1804 . Here, an insulator  1805  is formed in order to electrically insulate conductive vias v, internally connected to the second conductivity type semiconductor layer  1801 , from the first electrical connection portion  1804 , the first conductivity type semiconductor layer  1803 , and the active layer  1802 . In order to form an n-n junction, the second electrical connection portions  1807  of the first and second light-emitting structures C 1  and C 2  need to be connected to each other. For example, as shown in  FIG. 86 , conductive vias v, provided in first and second light-emitting structures C 1  and C 2 , may be connected to each other through a conductive substrate  1806 . Furthermore, as shown in  FIG. 87 , when an electrically insulating substrate  1806 ′ is used, the second electrical connection portion  1807  can connect conductive vias v, individually provided in first and second light-emitting structures C and C 2 , through a portion extended in parallel with the substrate  1806 ′. In addition to a connecting method using an electrical connection portion, a second conductivity type semiconductor layer  1801 ′ may be used according to a method similar to that described in  FIG. 88 . First and second light-emitting structures C 1  and C 2  may share the second conductivity type semiconductor layer  1801 ′. In this case, an n-n junction may be formed without separately connecting conductive vias v. 
     Finally,  FIGS. 89 through 91  are cross-sectional views schematically illustrating an example of a p-p junction. With reference to  FIGS. 89 through 91 , first and second light-emitting structures C 1  and C 2  forming a p-p junction are disposed on substrates  1906  and  1906 ′. The first and second light-emitting structures C 1  and C 2  each have a first conductivity type semiconductor layer  1903 , an active layer  1902 , and a second conductivity type semiconductor layer  1901  stacked upon each other in a sequential manner on a first electrical connection portion  1904 . Here, an insulator  1905  is formed in order that conductive vias v, individually internally connected to the second conductivity type semiconductor layer  1901 , are electrically insulated from the first electrical connection portion  1904 , the first conductivity type semiconductor layer  1903 , and the active layer  1902 . In order to form a p-p junction, the first electrical connection portions  1904  of the first and second light-emitting structures C 1  and C 2  need to be connected to each other. Here, the conductive vias v may be connected to another light-emitting structure (not shown), which forms the entire AC light emitting device. As an example of a p-p junction, as shown in  FIG. 89 , the first electrical connection portions  1904 , individually provided in the first and second light-emitting structures C 1  and C 2 , may be connected to each other through the substrate  1906  (not shown). Here, as shown in  FIG. 90 , when the substrate  1906 ′, having electrical insulation, is used, a connecting metallic layer  1908  is separately disposed to thereby connect the first electrical connection portions  1904  individually provided in the first and second light-emitting structures C 1  and C 2 . Alternatively, without employing a separate connecting metallic layer, as shown in  FIG. 91 , a configuration in which the first and second light-emitting structures C 1  and C 2  share the first electrical connection portion  1904  may also be employed. 
     A semiconductor light emitting device according to another exemplary embodiment of the invention will now be described with reference to  FIGS. 92 through 102 . 
       FIG. 92  is a cross-sectional view illustrating a vertical semiconductor light emitting device according to this embodiment.  FIGS. 93 and 94  are views illustrating a modified embodiment of the vertical semiconductor light emitting device of  FIG. 92 . 
     Referring to  FIG. 92 , a vertical semiconductor light emitting device  2000  according to this embodiment includes n-type and p-type semiconductor layers  2001  and  2003  and an active layer  2002  interposed therebetween, thereby forming a light-emitting structure. A reflective metal layer  2004  and a conductive substrate  2005  are formed under the light-emitting structure. An n-type electrode  2006  is formed on the n-type semiconductor layer  2001 , and a passivation layer  2007  having an uneven structure is formed to cover the side surfaces of the light-emitting structure. 
     The n-type semiconductor layer  2001  and the p-type semiconductor layer  2003  may be typically formed of nitride semiconductors. That is, the n-type semiconductor layer  2001  and the p-type semiconductor layer  2003  may be formed of semiconductor materials doped with an n-type impurity and a p-type impurity satisfying an equation of Al x In y Ga 1-x-y) N (where 0≤x≤1, 0≤y≤1, and 0≤x+y≤1 are satisfied), for example, GaN, AlGaN, and InGaN. The n-type impurity may include Si, Ge, Se, Te or the like. The p-type impurity may include Mg, Zn, Be, or the like. Meanwhile, an uneven structure may be formed on the upper surface of the n-type semiconductor layer  2001  in order to increase the efficiency of light being emitted in a vertical direction. 
     The active layer  2002 , formed between the n-type and p-type nitride semiconductor layers  2001  and  2003 , emits a predetermined amount of energy by electron-hole recombination and may have a multiple quantum well (MQW) structure in which quantum well layers and quantum barrier layers alternate with each other. As for the multiple quantum well structure, an InGaN/GaN structure may be widely used. 
     The first conductive contact layer  2004  may reflect light, emitted from the active layer  2002 , upward from the semiconductor light emitting device  2000 , and may be formed of Ag, Ni, Al, Rh, Pd, Ir, Ru, Mg, Zn, Pt, or Au. Here, though not illustrated in detail, the first conductive contact layer  2004  may have a dual or multi-layered structure to thereby increase reflection efficiency. For example, the first conductive contact layer  2004  may have a structure of Ni/Ag, Zn/Ag, Ni/Al, Zn/Al, Pd/Ag, Pd/Al, Ir/Ag, Ir/Au, Pt/Ag, Pt/Al, or Ni/Ag/Pt. However, in this embodiment, the reflective metal layer  2004  is not necessarily included. The reflective metal layer  2004  may also be removed. 
     The conductive substrate  2005  serves as a p-type electrode and a support holding the light-emitting structure, that is, the n-type semiconductor layer  201 , the active layer  2002 , and the p-type semiconductor layer  2003  during a laser-lift off process to be described below. Here, the conductive substrate  2005  may be formed of a material containing Si, Cu, Ni, Au, W, or Ti. Here, according to the selected material, the conductive substrate  2005  may be formed using plating or bonding. 
     The passivation layer  2007  is an insulating layer formed to protect the light-emitting structure, and particularly, the active layer  2002 . Further, the passivation layer  2007  is formed on a partially removed region of the light-emitting structure. Specifically, in addition to the side surfaces of the light-emitting structure, as shown in  FIG. 92 , the passivation layer  2007  may be formed on a portion of the upper surface of the n-type semiconductor layer  2001  and the upper surface of the reflective metal layer  2004 . Here, when the reflective metal layer  2004  is not used, the passivation layer  2007  is formed on the upper surface of the conductive substrate  2005 . When the side surfaces exposed by partially removing the light-emitting structure may be inclined upward as shown in  FIG. 92 , this structure may increase a light-emitting area and may further facilitate the formation of the passivation layer  2007 . 
     The passivation layer  2007  may be formed of a silicon oxide or a silicon nitride, such as SiO 2 , SiO x N y , or Si x N y , in order to perform a protection function, and may have a thickness of approximately 0.1 to 2 μm. Therefore, the passivation layer  2007  may have a refractive index of approximately 1.4 to 2.0. It may be difficult for light from the active layer  2002  to be emitted to the outside due to the difference in refractive index between the passivation layer  2007  and air or a molding structure of a package. In particular, in the vertical semiconductor light emitting device  2000  according to this embodiment, the p-type semiconductor layer  2003  has a relatively small thickness. For this reason, light, emitted toward the side of the active layer  2002 , can be emitted to the outside only when this light passes through the passivation layer  2007 . Since light, emitted in a lateral direction toward the passivation layer  2007  from the active layer  2002 , has a very small incidence angle with respect to the passivation layer  2007 , it becomes more difficult for the light to be emitted to the outside. 
     In this embodiment, an uneven structure is formed on the passivation layer  2007  to thereby increase external light extraction effects. In particular, as shown in  FIG. 92 , when the uneven structure is formed at a region through which the light, emitted in the lateral direction of the active layer  2002 , passes, the amount of light emitted towards the side of the vertical semiconductor light emitting device  2000  may be increased. Here, the region, through which light, emitted along the lateral direction of the active layer  2002 , passes, may be considered a region of the upper surface of the reflective metal layer  2004 , at which the light-emitting structure is not formed. According to simulation results, a configuration according to this embodiment has increased light extraction efficiency by approximately 5% or higher than another configuration having the same components except for the passivation layer  2007  employing the uneven structure. Meanwhile, though not necessarily required in this embodiment, the uneven structure of the passivation layer  2007  may also be formed on the upper surface of the n-type semiconductor layer  2001  to thereby increase vertical light extraction efficiency. 
     As shown in  FIGS. 93 and 94 , a region where an uneven structure of a passivation layer is formed may vary in order to maximize external light extraction effects. As shown in  FIG. 93 , an uneven structure may be formed to the side surfaces of a passivation layer  2007 ′. Furthermore, as shown in  FIG. 94 , an uneven structure may also be formed on a lower surface of the passivation layer  2007 ′, that is, a surface facing the reflective metal layer  2004 . Here, a pattern having a shape corresponding thereto may be formed on the reflective metal layer  2004 . 
       FIGS. 95 through 98  are cross-sectional views for describing a method of manufacturing a vertical semiconductor light emitting device having a structure described with reference to  FIG. 92 . 
     As shown in  FIG. 95 , an n-type semiconductor layer  2001 , an active layer  2002  and a p-type semiconductor layer  2003  are grown sequentially on a substrate  2008  for semiconductor single-crystal growth by using a process such as MOCVD, MBE, or HVPE. The substrate  2008  for semiconductor single-crystal growth may utilize sapphire, SiC, MgAl 2 O 4 , MgO, LiAlO 2 , LiGaO 2 , GaN or the like. In this case, the sapphire, a crystal having Hexa-Rhombo R3c symmetry, has lattice constants of 13.001 Å along the c-axis orientation and 4.758 Å along the a-axis orientation, respectively, and has a C(0001) plane, an A(1120) plane, and an R(1102) plane. In this case, since the C plane is stable at high temperatures and ensures the relatively easy growth of a nitride thin film, it is commonly used as a substrate for nitride growth. 
     Subsequently, as shown in  FIG. 96 , a reflective metal layer  2004  and a conductive substrate  2005  are formed on the p-type semiconductor layer  2003  using a method such as plating or sub-mount bonding. Thereafter, although not shown in detail, the substrate  2008  for semiconductor single crystal growth is removed using an appropriate lift-off process such as laser lift-off or chemical lift-off. 
     Thereafter, as shown in  FIG. 97 , a resultant light emitting structure is partially removed for the purpose of dicing it in the unit of devices and forming a passivation layer. In this case, a side surface exposed by the removal may be sloped upward. Furthermore, a process such as wet etching is performed on the top surface of the n-type semiconductor layer  2001 , which is exposed by the removal of the substrate for semiconductor signal crystal growth, thereby forming an uneven structure that is contributive to enhancing light extraction efficiency in a vertical direction. 
     Thereafter, as shown in  FIG. 98 , a passivation layer  2007  for protecting the light emitting structure is formed. This process may be carried out by appropriately depositing, for example, a silicon oxide or a silicon nitride. An uneven structure may be formed in the light emitting surface of the passivation layer  2007  to thereby enhance luminous efficiency in a lateral direction. In this case, this uneven structure may be formed by appropriately using a dry-etching or wet-etching process known in the art. Also, if necessary, the uneven structure may formed even in another light emitting surface of the passivation layer  2007 . After the formation of the passivation layer  2007 , an n-type electrode is formed on the top surface of the n-type semiconductor layer  2001 , thereby completing a structure illustrated in  FIG. 92 . 
     The present invention provides a semiconductor light emitting device having a modified structure from the above vertical structure in order to further enhance electrical characteristics and optical characteristics. 
       FIG. 99  is a schematic cross-sectional view illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention. Referring to  FIG. 99 , a semiconductor light emitting device  2100 , according to this embodiment, includes a conductive substrate  2105 , a light emitting structure including a first conductivity type semiconductor layer  2103 , an active layer  2102  and a second conductivity type semiconductor layer  2101  sequentially formed on the conductive substrate  2105 , a second conductivity type electrode  2106  applying an electrical signal to the second conductivity type semiconductor layer  2101 , and a passivation layer  2107  having an uneven structure and disposed on the side surface of the light emitting structure. In  FIG. 99 , the active layer  2102  is placed on a relatively upper level as compared to the structure shown in  FIG. 92  or the like. However, the active layer  2102  may be placed at various locations, and may, for example, be located at a similar height to that of the lower portion of the passivation layer  2107 . 
     In the previous embodiment, that is, in the vertical semiconductor light emitting device, the n-type electrode is formed on the surface of the n-type semiconductor layer exposed when removing the sapphire substrate. However, according to this embodiment, an n-type electrode is exposed to the outside from under the n-type semiconductor layer by using a conductive via. In detail, the second conductivity type electrode  2106  includes conductive vias v penetrating the first conductivity type semiconductor layer  2104  and the active layer  2102  and connected to the second conductivity type semiconductor layer  2101  within the second conductivity type semiconductor layer  2101 , and an electrical connection portion P extending therefrom and exposed to the outside of the light emitting structure. In this case, the second conductivity type electrode  2106  needs to be electrically separated from the conductive substrate  2105 , the first conductivity type semiconductor layer  2103 , and the active layer  2102 . Therefore, an insulator  2108  is formed appropriately around the second conductivity type electrode  2106 . Any material having a low level of electrical conductivity is usable as the insulator  2108 ; however, a material with a low level of light absorbency is preferred. For example, the insulator  2108  may be formed of the same material as the passivation layer  2107 . 
     The second conductivity type electrode  2106  may be formed of a metallic material that can form an ohmic-contact with the second conductivity type semiconductor layer  2101 . Also, the second conductivity type electrode  2106  may be formed entirely of the same material. Alternatively, the electrical connection portion P may be formed of a different material from another part of the second conductivity type electrode  2106 , in consideration of the fact that the electrical connection portion P may be used as a bonding pad portion. Regarding the previously described manufacturing process, the first and second conductivity type semiconductor layers  2101  and  2103  may be p-type and n-type semiconductor layers in general, but the present invention is not limited thereto. As shown in  FIG. 99 , a first contact layer  2104  may be formed as an additional element between the first conductivity type semiconductor layer  2103  and the conductive substrate  2105 , and may utilize a metal having a high level of reflectivity, such as Ag or Al. In this case, the first contact layer  2104  and the second conductivity type electrode  2106  are electrically separated from each other by the insulator  2108 . 
     The above electrical connection structure allows the second conductivity type semiconductor layer  2101  to receive an electrical signal from its inside rather than from above. Notably, no electrode is formed on the second conductivity type semiconductor layer  2101 , thereby achieving an increase in light emitting area. In addition, the conductive vias V, formed in the second conductivity type semiconductor layer  2101 , may contribute to enhancing a current spreading effect. In this case, desired electrical characteristics can be attained by appropriately controlling, for example, the number, area and shape of the conductive vias V. According to this embodiment, the main process such as the formation of the conductive substrate, the removal of the sapphire substrate or the like adopts the process of manufacturing a vertical semiconductor light emitting device, but the device shape obtained by such process is rather similar to a horizontal structure. In this regard, the structure according to this embodiment may be referred to as a combination structure of vertical and horizontal structures. 
     As in the previous embodiment, the passivation layer  2107  is formed on the side surface or the like of the light emitting structure, and has an uneven structure on the path of light emitted from the active layer  2102 , thereby enhancing the extraction efficiency of light emitted in a lateral direction from the active layer  2102  toward the passivation layer  2107 . Furthermore, as shown in  FIG. 99 , an uneven structure may also be formed on the top surface of the second conductivity type semiconductor layer  2101 . Although not shown, an uneven portion may also be formed on the sloped side surface of the passivation layer  2107 . 
       FIG. 100  is a schematic cross-sectional view illustrating a semiconductor light emitting device having a modified structure of that depicted in  FIG. 99 . An exemplary embodiment depicted in  FIG. 100  further includes an etch stop layer  2109  in the structure depicted in  FIG. 99 . Thus, only the etch stop layer  2109  will now be described. The etch stop layer  2109  is formed on a portion of at least the conductive substrate  2105  on which the light emitting structure is absent, and is formed of a material (e.g., an oxide such as SiO 2 ) that shows a different etching characteristic for a specific etching method from a semiconductor material (e.g., a nitride semiconductor) used in the light emitting structure. An etching depth can be controlled by the etch stop layer  2109  since the light emitting structure can be etched only up to a region where the etch stop layer  2109  is located. In this case, the etch stop layer  2109  and the insulator  2108  may be formed of the same material for ease of the process. When the light emitting structure is etched in order to, for example, expose the second conductivity type electrode  2106  to the outside, this may result in current leakage due to the deposition of the material of the conductive substrate  2105  or the first contact layer  2104  on the side surface of the light emitting structure. Therefore, the etch stop layer  2109  is formed in advance under the light emitting structure, which is to be removed by etching, thereby minimizing the above-mentioned problem. 
       FIG. 101  is a schematic cross-sectional view illustrating a semiconductor light emitting device according to another exemplary embodiment of the present invention.  FIG. 102  illustrates a structure further including an etch stop layer in the structure depicted in  FIG. 101 . Referring to  FIG. 101 , a semiconductor light emitting device  2200 , according to this embodiment, includes a conductivity substrate  2205 , a light emitting structure that includes a first conductivity type semiconductor layer  2203 , an active layer  2202  and a second conductivity type semiconductor layer  2201  sequentially formed on the conductive substrate  2205 , a first contact layer  2204  applying an electrical signal to the first conductivity type semiconductor layer  2203 , conductive vias v extending from the conductive substrate  2205  up to the inside of the second conductivity type semiconductor layer  2201 , and a passivation layer  2207  formed on the side surface of the light emitting structure and having an uneven structure. 
     As for differences from the structure described with reference to  FIG. 99 , the conductive substrate  2205  is electrically connected with the second conductivity type semiconductor layer  2201 , and the first contact layer  2204  connected with the first conductivity type semiconductor layer  2203  includes an electrical connection portion P and is thus exposed to the outside. The conductive substrate  2205  may be electrically separated from the first contact layer  2204 , the first conductivity type semiconductor layer  2203 , and the active layer  2202  by an insulator  2208 . That is, this embodiment of  FIG. 101  has a structural difference from the embodiment of  FIG. 99  in that, in  FIG. 101 , the first contact layer  2204 , connected with the first conductivity type semiconductor layer  2203 , is exposed to the outside to thereby provide the electrical connection portion P, whereas, in  FIG. 99 , the second conductivity type electrode  2106 , connected with the second conductivity type semiconductor layer  2101 , is exposed to the outside to thereby provide the electrical connection portion P. Effects obtained from this structure other than this difference regarding electrical connections are identical to those described with reference to  FIG. 99 . As shown in  FIG. 102 , an etch stop layer  2209  may also be provided. However, the structure in which the first contact layer  2204  is exposed to the outside according to this embodiment depicted in  FIG. 101  may actually facilitate the process of forming the insulator  2208 , as compared to the embodiment depicted in  FIG. 99 . 
     Light Emitting Device Package and Light Source Module 
     A light emitting device package, according to the present invention, includes the above semiconductor light emitting device. 
     Hereinafter, a light emitting device package including a semiconductor light emitting device will be described according to various exemplary embodiments of the present invention. 
       FIG. 103  is a schematic view illustrating a white light emitting device package according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 103 , a white light emitting device package  3010 , according to this embodiment, includes a blue light emitting device  3015 , and a resin encapsulant  3019  encapsulating the blue light emitting device  3015  and having an upwardly convex lens shape. 
     The resin encapsulant  3019 , employed in this embodiment, is illustrated as having a hemispheric lens shape for ensuring a wide orientation. The blue light emitting device  3015  may be mounted directly onto a separate circuit board. The resin encapsulant  3019  may be formed of a silicon resin, an epoxy resin or a combination thereof. Green phosphors  3012  and red phosphors  3014  are dispersed within the resin encapsulant  3019 . 
     The green phosphor  3012 , applicable to this embodiment, may be at least one selected from the group consisting of a silicate-based phosphor of M 2 SiO 4 :Eu,Re, a sulfide-based phosphor of MA 2 D 4 :Eu,Re, a phosphor of β-SiAlON:Eu,Re, and an oxide-based phosphor of M′A′ 2 O 4 :Ce,Re′. 
     Here, M denotes at least two elements selected from the group consisting of Ba, Sr, Ca and Mg, A denotes at least one selected from the group consisting of Ga, Al and In, D denotes at least one selected from the group consisting of S, Se and Te, M′ denotes at least one selected from the group consisting of Ba, Sr, Ca and Mg, A′ denotes at least one selected from the group consisting of Sc, Y, Gd, La, Lu, Al and In, Re denotes at least one selected from the group consisting of Y, La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I, and Re′ denotes at least one selected from the group consisting of Nd, Pm, Sm, Tb, Dy, Ho, Er, Tm, Yb, F, Cl, Br and I. Furthermore, Re and Re′ are added at 1 ppm to 50000 ppm in amount. 
     The red phosphors  3014 , applicable to this embodiment, are at least one selected from the group consisting of nitride-based phosphors of M′AlSiN x :Eu,Re (1≤x≤5) and sulfide-based phosphors of M′D:Eu,Re. 
     Here, M′ denotes at least one selected from the group consisting of Ba, Sr, Ca and Mg, D denotes at least one selected from the group consisting of S, Se and Te, A′ denotes at least one selected form the group consisting of Sc, Y, Gd, La, Lu, Al and In, Re denotes at least one selected from the group consisting of Y, La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I. Re is added at 1 ppm to 50000 ppm. 
     According to the present invention, specific green phosphors and specific red phosphors are combined in due consideration of a half amplitude, a peak wavelength and/or conversion efficiency, so that white light having a high color rendering index of 70 or higher can be provided. Since light in various wavelength bands is obtained by multiple phosphors, color reproducibility can be enhanced. 
     The dominant wavelength of the blue light emitting device may range from 430 nm to 455 nm. In this case, in order to increase a color rendering index by ensuring a wide spectrum in a visible light band, the peak wavelength of light, emitted from the green phosphors  3012 , may range from 500 nm to 550 nm, and the peak wavelength of light, emitted from the red phosphors  3014 , may range from 610 nm to 660 nm. 
     The blue light emitting device may have an half amplitude ranging from 10 nm to 30 nm, and the green phosphors may have a half amplitude ranging from 30 nm to 100 nm, and the red phosphors may have a half amplitude ranging from 50 nm to 150 nm. 
     According to another exemplary embodiment of the present invention, yellow or yellowish orange phosphors may be used in addition to the red phosphors  3014  and the green phosphors  3012 . This may ensure an improved color rendering index. An associated embodiment is illustrated in  FIG. 104 . 
     Referring to  FIG. 104 , a white light emitting device package  3020 , according to this embodiment, includes a package body  3021  having a reflective cup in its center, a blue light emitting device  3025  mounted on the bottom of the reflective cup, and a transparent resin encapsulant  3029  encapsulating the blue light emitting device  3025  in the reflective cup. 
     The resin encapsulant  3029  may be formed of, for example, a silicon resin, an epoxy resin or a combination thereof; however, the invention is not limited thereto. According to this embodiment, the resin encapsulant  3029  contains yellow phosphors or yellowish orange phosphors  3026  in addition to green phosphors  3022  and red phosphors  3012  that are the same as those described with reference to  FIG. 103 . 
     That is, the green phosphors  3022  may be at least one selected from the group consisting of silicate-based phosphors of M 2 SiO 4 :Eu,Re, sulfide-based phosphors of MA 2 D 4 :Eu,Re, phosphors of β-SiAlON:Eu,Re, and oxide-based phosphors of M′A′ 2 O 4 :Ce,Re′. The red phosphors  3024  may be at least one of nitride-based phosphors of M′AlSiN x :Eu,Re(1≤x≤5) and sulfide-based phosphors of M′D:Eu,Re. 
     According to this embodiment, third phosphors  3026  are further included. The third phosphors may be yellow or yellowish orange phosphors that can emit light within an intermediate wavelength band between green and red light wavelength bands. The yellow phosphors may be silicate-based phosphors, and the yellowish orange phosphors may be phosphors of a-SiAlON:Eu,Re. 
     According to the exemplary embodiments above, two or more kinds of phosphor powders are mixed and dispersed in a single resin encapsulant region; however they may be variously modified in structure. In greater detail, the two or three kinds of phosphors may be provided in respectively different layers. For example, the green phosphors, the red phosphors and the yellow or yellowish orange phosphors may be provided as a multilayer phosphor structure by distributing powders thereof under high pressure. 
     Alternatively, the phosphor structure may be implemented as multilayer phosphor-containing resin layers. 
     Referring to  FIG. 105 , a white light emitting device package  3030 , according to this embodiment, includes a package body  3031  having a reflective cup in its center, a blue light emitting device  3035  mounted on the bottom of the reflective cup, and a transparent resin encapsulant  3039  encapsulating the blue light emitting device  3035  in the reflective cup, as in the previous embodiment. 
     Resin layers, each containing different kinds of phosphors, are provided on the resin encapsulant  3039 . That is, a wavelength conversion part may be configured such that it has a first resin layer  3032  containing the green phosphors, a second resin layer  3034  containing the red phosphors, and a third resin layer  30306  containing the yellow or yellowish orange phosphors. 
     The phosphors used in this embodiment may be identical or similar phosphors to those described with reference to  FIG. 104 . 
     White light, obtained by the combination of the phosphors proposed by the present invention, can ensure a high rendering index. This will now be described in more detail with reference to  FIG. 106 . 
     Referring to  FIG. 106 , in a related-art example, yellow phosphors are combined with a blue light emitting device, thereby obtaining converted yellow light as well as light in a blue wavelength band. Since the overall visible light spectrum contains virtually no light from the green and red wavelength bands, it is difficult to ensure a color rendering index close to natural light. Notably, the converted yellow light has a small half-amplitude in order to achieve high conversion efficiency, which further lowers the color rendering index. 
     Comparative to the above, in an inventive example, green phosphors G and red phosphors R are combined with a blue light emitting device. Since light is emitted in green and red wavelength bands, unlike in the case of the comparative example, a wider spectrum can be obtained in the visible light band, thereby significantly enhancing a color rendering index. Additionally, the color rendering index can be further enhanced by adding yellow or yellowish orange phosphors that can emit light in an intermediate wavelength band between the green and red wavelength bands. 
     With reference to  FIGS. 107A through 109B , the green phosphors, the red phosphors, and the selectively added yellow and yellowish orange phosphors, employed in the present invention, will now be described. 
       FIGS. 107A through 109B  illustrate the wavelength spectrums of phosphors proposed by the present invention, regarding light generated from a blue light emitting device (about 440 nm). 
       FIGS. 107A through 107D  illustrate spectrums regarding green phosphors employed in the present invention. 
     First,  FIG. 107A  illustrates the spectrum of silicate-based phosphors of M 2 SiO 4 :Eu,Re where M denotes at least two selected from the group consisting of Ba, Sr, Ca and Mg, Re denotes at least one selected from the group consisting of Y, La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I, and Re is in the range of 1 ppm to 50,000 ppm. Converted green light has a peak wavelength of about 530 nm, and a half amplitude of about 65 nm. 
       FIG. 107B  illustrates the spectrum of oxide-based phosphors of M′A′ 2 O 4 :Ce,Re′, where M′ denotes at least one selected from the group consisting of Ba, Sr, Ca and Mg, A′ denotes at least one selected from the group consisting of Sc, Y, Gd, La, Lu, Al and In, Re′ is at least one selected from the group consisting of Nd, Pm, Sm, Tb, Dy, Ho, Er, Tm, Yb, F, Cl, Br and I, and Re′ is in the range of 1 ppm to 50,000 ppm. Converted green light has a peak wavelength of about 515 nm, and a half amplitude of about 100 nm. 
       FIG. 107C  illustrates the spectrum of sulfide-based phosphors of MA 2 D 4 :Eu,Re where M denotes at least two selected from the group consisting of Ba, Sr, Ca and Mg, A denotes at least one selected from the group consisting of Ga, Al and In, D denotes at least one selected from the group consisting of S, Se and Te, Re denotes at least one selected from the group consisting of La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I, and Re is in the range of 1 ppm to 50,000 ppm. Converted green light has a peak wavelength of about 636 nm and a half amplitude of about 60 nm. 
       FIG. 107D  illustrates the spectrum of phosphors of β-SiAlON:Eu,Re where Re denotes at least one selected from the group consisting of Y, La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I, and Re is in the range of 1 ppm to 50,000 ppm. Converted green light has a peak wavelength of about 540 nm, and a half amplitude of about 45 nm. 
       FIGS. 108A and 108B  illustrate the spectrums of red phosphors employed in the present invention. 
       FIG. 108A  illustrates the spectrum of nitride-based phosphors of M′AlSiN x :Eu,Re (1≤x≤5) where M′ denotes at least one selected from the group consisting of Ba, Sr, Ca and Mg, Re denotes at least one selected from the group consisting of Y, La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I, and Re is in the range of 1 ppm to 50,000 ppm. Converted red light has a peak wavelength of about 640 nm, and a half amplitude of about 85 nm. 
       FIG. 108B  illustrates the spectrum of sulfide-based phosphors of M′D:Eu,Re where M′ denotes at least one selected from the group consisting of Ba, Sr, Ca and Mg, D denotes at least one selected from the group consisting of S, Se and Te, Re denotes at least one selected from the group consisting of Y, La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I, and Re is in the range of 1 ppm to 50000 ppm. Converted red light has a peak wavelength of about 655 nm and a half amplitude of about 55 nm. 
       FIGS. 109A and 109B  illustrate the spectrums of yellow or yellowish orange phosphors selectively employed in the present invention. 
       FIG. 109A  illustrates the spectrum of silicate-based phosphors. Converted yellow light has a peak wavelength of about 555 nm and a half amplitude of about 90 nm. 
       FIG. 109B  illustrates the spectrum of phosphors of a-SiAlON:Eu,Re where Re denotes at least one selected from the group consisting of Y, La, Ce, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, F, Cl, Br and I, and Re is in the range of 1 ppm to 50,000 ppm. Converted yellow light has a peak wavelength of about 580 nm and a half amplitude of about 35 nm. 
     According to the present invention, specific green phosphors and specific red phosphors are combined or yellow or yellowish orange phosphors are added to this combined phosphors in consideration of the half amplitude, the peak wavelength and/or conversion efficiency. Accordingly, white light having a high color rendering index of 70 or higher can be provided. 
     When the dominant wavelength of the blue light emitting device ranges from 430 nm to 455 nm, the peak wavelength of light emitted from the green phosphors may range from 500 nm to 550 nm, and the peak wavelength of light emitted from the red phosphors may range from 610 nm to 660 nm. The peak wavelength of light emitted from the yellow or yellowish orange phosphors may range from 550 nm to 600 nm. 
     When the blue light emitting device has a half amplitude ranging from 10 nm to 30 nm, the green phosphors may have a half amplitude ranging from 30 nm to 100 nm, and the red phosphors may have a half amplitude ranging from 50 nm to 150 nm. The yellow or yellowish orange phosphors may have a half amplitude ranging from 20 nm to 100 nm. 
     According to the present invention, a wide spectrum can be ensured in a visible light band according to the selections and combinations of the phosphors, and superior white light having a higher color rendering index can be provided. 
     Such a light emitting device package may provide a white light source module that can be useful as a light source for an LCD backlight unit. Namely, the white light source module, according to this embodiment, may constitute a backlight assembly as a light source for an LCD backlight unit by being combined with various optical members such as a diffusing plate, a light guide plate, a reflective plate and a prism sheet.  FIGS. 110 and 111  illustrate such white light source module. 
     Referring to  FIG. 110 , a light source module  3100  for an LCD backlight includes a circuit board  3101  and an array of a plurality of white light emitting device packages mounted on the circuit board  3101 . A conductive pattern (not shown), connected with LED devices  3010 , may be formed on the top surface of the circuit board  3101 . 
     Each of the white light emitting device packages  3010  may be understood as a white light emitting device package described with reference to  FIG. 103 . That is, the blue light emitting device  3015  is mounted directly on the circuit board  3101  by using a chip-on-board (COB) method. Each of the white light emitting device packages  3010  includes the hemispherical resin encapsulant  3019  equipped with a lens function and having no separate reflective wall, thereby attaining a wide angle of orientation. The wide angle of orientation of each white light source may contribute to reducing the size (thickness or width) of an LCD. 
     Referring to  FIG. 111 , a light source module  3200  for an LCD backlight includes a circuit board  3201  and an array of a plurality of white light emitting device packages  3020  mounted on the circuit board  3201 . As described above with reference to  FIG. 104 , the white light emitting device package  3020  includes the blue light emitting device  3025  mounted in the reflective cup of the package body  3021 , and the resin encapsulant  3029  encapsulating the blue light emitting device  3025 . The resin encapsulant  3029  may contain the yellow or yellowish orange phosphors  3026  dispersed therein, as well as the green and red phosphors  3022  and  3024 . 
       FIG. 112  is a cross-sectional view illustrating a light emitting device package according to another exemplary embodiment of the present invention. 
     Referring to  FIG. 112 , a light emitting device package  400 , according to this embodiment, includes a light emitting device  4011 , electrode structures  4012  and  4013 , a package body  4015 , a transmissive transparent resin  4016  and a recess  4018  on which the light emitting device  4011  is mounted. 
     The light emitting device  4011  is bonded and connected with one set of the ends of the (metallic) wires  4014   a  and  4014   b . The electrode structures  4012  and  4013  are bonded and connected with the other set of the ends of the pair of wires  4014   a  and  4014   b , respectively. 
     Here, the light emitting devices according to the above-described exemplary embodiment of the present invention may be used as the light emitting device  4011  of this embodiment. 
     The package body  4015  is a molded structure obtained by injecting-molding a resin material, and includes a cavity  4016  having a closed bottom and an open top. 
     Here, the cavity  4017  has an upper slope surface inclined at a predetermined angle. A reflective member  4017   a , formed of a metallic material having a high reflectivity such as Al, Ag or Ni, may be provided on the upper slope surface so as to reflect light generated from the reflective member  4017   a.    
     The package body  4015  is fixed by the pair of electrode structures  4012  and  4013  molded integrally with the package body  4015 . The top surface of each of the electrode structures  4012  and  4013  has one end portion exposed to the outside through the bottom of the cavity  4017 . 
     The other end portion of each of the electrode structures  4012  and  4013  is exposed to the outside of the package body  4015  and is connected with an external power source. 
     The recess  4018  is formed by downwardly recessing the top surfaces of the electrode structures  4012  and  4013 , exposed in the bottom of the cavity  4017 , to a predetermined depth. Here, the recess  4018  may be formed in one electrode structure  4012  of the pair of electrode structures  4012  and  4013  on which the light emitting device  4011  is mounted. 
     The recess  4018  is provided in the form of a downwardly bent portion at one end portion of the electrode structure  4012  where at least one light emitting device  4011  is mounted. This bent portion includes a flat mounting surface on which the light emitting device  4011  is mounted, and a pair of lower slope surfaces respectively extending upward at a predetermined angle from the left and right sides of the mounting surface and facing the outer surface of the light emitting device  4011 . 
     The lower slope surfaces  4012   a  and  4013   a  may be provided with a reflective member to reflect light generated from the light emitting device  4011 . 
     The recess  4018  may formed at a depth H ranging from 50 μm to 400 μm in due consideration of the height h of the mounted light emitting device  4011 . This may reduce the height H of the cavity  4017  of the package body up to 150 μm to 500 μm, and also reduce the amount of transmissive transparent resin filled in the cavity  4017 . Accordingly, manufacturing costs can be reduced, light intensity can be enhanced, and a reduction in the overall size of products can be achieved. 
       FIG. 113  is a cross-sectional view illustrating a light emitting device package according to a modified embodiment from the embodiment illustrated in  FIG. 112 . 
     As shown in  FIG. 113 , the light emitting device package, according to this modified embodiment, includes a hole  4018   a  instead of the recess  4018 , between the opposing end portions of the pair of electrode structures  4012  and  4013 . The hole  4018   a  is formed by recessing the bottom of the cavity  4017  to a predetermined depth when the package body  4015  is molded. 
     In this modified embodiment, elements other than the hole  4018   a  are identical to those of the light emitting device package according to the exemplary embodiment of  FIG. 112 , and the descriptions thereof will be omitted. 
     The transmissive transparent resin  4016  is formed of a transparent resin material such as epoxy, silicon or resin. Such a transparent resin material is filled in the cavity  4017  in order to cover and protect the light emitting device  4011  and wires  4014   a  and  4014   b  against external conditions. 
     Here, the transmissive transparent resin  4016  may include one of wavelength converting phosphors among YAG-, TAG-, silicate-, sulfide- or nitride-based phosphors capable of converting light, generated from the light emitting device  4011 , into white light. 
     The YAG- and TAG-based phosphors may be selected from (Y, Tb, Lu, Sc, La, Gd, Sm)3(Al, Ga, In, Si, Fe)5(O,S)12:Ce, and the silicate-based phosphors may be selected from (Sr, Ba, Ca, Mg)2SiO4: (Eu, F, Cl). The sulfide-based phosphors may be selected from (Ca,Sr)S:Eu, (Sr,Ca,Ba)(Al,Ga)2S4:Eu. The nitride-based phosphors may be selected from phosphor components of (Sr, Ca, Si, Al, O)N:Eu (e.g., CaAlSiN4:Eu β-SiAlON:Eu) or Ca-α SiAlON:Eu-based (Cax,My)(Si,Al)12(O,N)16 where M denotes at least one of Eu, Tb, Yb and Er, 0.05&lt;(x+y)&lt;0.3, 0.02&lt;x&lt;0.27 and 0.03&lt;y&lt;0.3. 
     The white light may be generated by combining a blue (B) light emitting device with yellow (Y) phosphors, green (G) and red (R) phosphors, or yellow (Y), green (G) and red (R) phosphors. The yellow, green and red phosphors are excited by the blue light emitting device to thereby respectively emit yellow light, green light and red light. The yellow light, the green light and the red light are mixed with a part of blue light emitted from the blue light emitting device, so that the white light is output. 
     A detailed description of those phosphors for white-light output has been made in detail in the above-described embodiments, and thus is omitted in this modified example. 
     Lower slope surfaces  4012   b  and  4013   b  may be formed at the end portions of the electrode structures  4012  and  4013  facing the outer surface of the light emitting device  4011  mounted in the hole  4018   a . In this case, a reflective member is provided on the lower slope surfaces  4012   b  and  4013   b  and reflects light emitted from the light emitting device  4011 . 
     As for the light emitting device packages  4000  and  4000 ′, the light emitting device  4011  disposed at the very center of the cavity  4017  is mounted on the mounting surface of the recess formed by downwardly bending the electrode structure  4012 , or in the hole  4018   a  formed between the opposing end portions of the electrode structures  4012  and  4013 . Accordingly, the top surface of the light emitting device  4011 , wire-bonded with the electrode structures  4012  and  4013  using the wires  4014   a  and  4014   b , may be located on roughly the same level as the top surfaces of the electrode structures  4012  and  4013 . 
     Accordingly, the maximum height of the wires  4014   a  and  4014   b  wire-bonded with the light emitting device  4011  can be lowered by the lowered mounting height of the light emitting device  4011 . 
     This reduction in height ensures a reduction in the amount of transmissive transparent resin  4016  filled in the cavity to protect the light emitting device  4011  and the wires  4014   a  and  4014   b . Also, the filling height H of the transmissive transparent resin  4016  can be decreased by the reduced height of the mounted light emitting device  4011 . Accordingly, the intensity of light, emitted from the light emitting device  4011 , can be enhanced relative to the related art. 
     Since the filling height H of the transmissive transparent resin  4016  in the cavity  4017  is lowered, the level of the top of the package body  4015  is lowered by the lowered filling height. Thus, a reduction in the overall size of the package can be achieved. 
       FIGS. 114A through 114C  are schematic views illustrating the process of an external lead frame in the light emitting device package according to this embodiment. 
     As shown in  FIG. 114A , the electrode structures  4012  and  4013 , which are respectively cathode and anode electrodes, are fixed integrally to the package body  4015  injection-molded mostly using a resin material. However, their end portions are exposed to the outer side of the package body  4015  and connected with an external power source. 
     The electrode structures  4012  and  4013 , downwardly exposed to the outside of the package body  4015 , are bent toward the side surface and/or the bottom surface of the package body such that the electrode structures  4012  and  4013  are bent in an opposite direction to the light emitting surface where the cavity  4017  is formed. 
     The electrode structures  4012  and  4013  are bent toward the side surface and/or the back surface (rear or lower portion) of the mounting surface (bottom surface  4019 ) of the package. 
     As for the process of forming such electrode structures  4012  and  4013 , as shown in  FIG. 114B , the end portion of the exposed electrode structure  4012  is bent first to conform with the shape of the side surface of the package  4000 , and is then bent rearward of the bottom  4019  of the package to thereby complete the overall shape of the electrode structure  4012  as shown in  FIG. 114B . 
     Hereinafter, a method of manufacturing β-sialon phosphors among the above-described phosphors, which can be regulated to have high light intensity and desired particle characteristics. 
     The method of manufacturing β-sialon phosphors according to the present invention relates to manufacturing β-sialon phosphors having a chemical formula expressed as Si (6-x) Al x O y N (6-y) :Lnz where Ln is a rare-earth element and 0&lt;x≤4.2, 0&lt;y≤4.2 and 0&lt;z≤1.0 are satisfied. The method of manufacturing the β-sialon phosphors includes: preparing a raw-material mixture by mixing a base raw material with an activator raw material activating the base raw material, the base raw material including a silicon raw material containing metal silicon, and an aluminum raw material including at least one of metal aluminum and an aluminum compound; and heating the raw-material mixture in a nitrogen atmosphere 
     According to the present invention, raw materials are mixed and heated in a nitrogen atmosphere to thereby manufacture β-sialon phosphors. The raw materials include silicon, aluminum and a rare-earth metal acting as an activator. 
     The silicon raw material refers to a raw material containing silicon, and may include only metal silicon or both metal silicon and a silicon compound mixed therewith. The silicon compound may utilize silicon nitride or silicon oxide. 
     The metal silicon may be high-purity metal silicon that is in a powder phase with a low content of impurities such as Fe. In the case of metal silicon powder, the particle size or distribution thereof do not have a direct influence on the particle composition of phosphors. However, depending on the firing conditions or the raw material being mixed, the particle size or distribution of the silicon powder affects particle characteristics such as the particle size and the shape of phosphors, and also affects the light emitting characteristic of the phosphors. In this regard, the particle size of the metal silicon powder may be 300 μm or less. 
     Regarding reactivity, the smaller the particle size of the metal silicon is, the higher the reactivity becomes. However, since the reactivity is also affected by a raw material being mixed or a firing rate, the metal silicon does not necessarily have a small particle size, and is not limited to the powder phase. 
     The aluminum raw material may include metal aluminum, an aluminum compound containing aluminum or both. The aluminum compound containing aluminum may be, for example, aluminum nitride, aluminum oxide or aluminum hydroxide. In the event that the metal silicon is used as the silicon raw material, the aluminum raw material does not need to utilize metal aluminum and may utilize only the aluminum compound. 
     In the event that the metal aluminum is used, high-purity metal aluminum that is in a powder phase with a low content of impurities such as Fe may be used. Regarding the above-described viewpoint, the metal aluminum may have a particle size of 300 μm or less. However, since raw materials being mixed or a firing rate have their influence even in the case of the metal aluminum, the metal aluminum does not necessarily have a small particle size, and is not limited to the powder phase. 
     The activator raw material may utilize a rare-earth metal selected from the group consisting of Eu, Ce, Sm, Yb, Dy, Pr, and Tb. In detail, an example thereof may include an oxide such as Eu 2 O 3 , Sm 2 O 3 , Yb 2 O 3 , CeO, Pr 7 O 11  or Tb 3 O 4 , Eu(NO 3 ) 3 , or EuCl 3 . Preferably, the activator raw material may be Eu or Ce. 
     By controlling a mixing ratio between the silicon raw material and the aluminum raw material, the particle characteristic of the β-sialon phosphors may be controlled. Furthermore, the particle characteristic of the β-sialon phosphors may be controlled by controlling a mixing ratio between the silicon compound and the metal silicon of the silicon raw material, or a mixing ratio between the aluminum compound and the metal aluminum of the aluminum raw material. The effects of the raw materials of the metal silicon or the metal aluminum will be described in greater detail through inventive examples that will be described later. 
     The β-sialon phosphors, manufactured according to the present invention, may have the following chemical formula 1:
 
Si(6- x )Al x O y N(6- y ):L nz   Chemical formula 1
 
where Ln is a rare-earth element, and 0&lt;x≤4.2, 0&lt;y≤4.2, and 0&lt;z≤1.0 are satisfied. The β-sialon phosphors may be green light emitting phosphors, and the peak wavelength thereof may range from 500 nm to 570 nm.
 
     As described above, the activator raw material, containing a rare-earth element such as Eu, Sm, Yb, Ce, Pr of Tb as an activator, is measured and mixed to the silicon raw material containing the metal silicon, and the aluminum raw material containing at least one of the metal aluminum and the aluminum compound. Thereafter, a boron nitride (BN) crucible is filled with this raw-material mixture and is fired at high temperature under a nitrogen atmosphere, thereby manufacturing β-sialon phosphors. 
     Phosphors are produced from the raw-material mixture by being fired at a high temperature in the nitrogen atmosphere. Here, the N 2  concentration in the nitrogen atmosphere may be 90% or higher. Also, the gas pressure in the nitrogen atmosphere may range from 0.1 Mpa to 20 Mpa. To create the nitrogen atmosphere, a vacuum state may be formed and a nitrogen atmosphere may be then introduced. Alternatively, the nitrogen atmosphere may be introduced without forming a vacuum state, and it may be introduced discontinuously. 
     When the raw-material mixture including the metal silicon is fired in the nitrogen atmosphere, nitrogen reacts with silicon and thus nitrides the silicon to thereby form sialon, so that the nitrogen gas serves as a nitrogen supply source. At this time, since the silicon, aluminum and the activator raw material react together before or during the nitriding process, sialon with a uniform composition can be manufactured. In such a manner, the light intensity of the produced β-sialon phosphors can be improved. 
     Heating in this firing process may be conducted at a high temperature ranging from 1850° C. to 2150° C. This heating temperature may be varied according to the composition of the raw material. However, to produce phosphors having high light intensity, the firing may be carried out at a high temperature ranging from 1900° C. to 2100° C. under a gas pressure of 0.8 Mpa or higher. After the heating process, milling or classification may be performed in order to control the particle characteristics of the heated raw-material mixture. The milled or classified raw-material compound may be re-fired at a high temperature. 
     Hereinafter, the present invention will now be described in greater detail with reference to inventive examples of producing β-sialon phosphors using the method of manufacturing β-sialon phosphors according to the present invention. 
     In the following exemplary embodiments, raw materials are made into a mixture by measuring predetermined amounts of activator raw material as well as silicon and aluminum raw materials, which are the base raw materials, and mixing them using a ball mill or a mixer. The resultant raw-material mixture is put into a high-temperature-resistant container such as a BN crucible and is then put into an electric furnace where pressure-firing or vacuum-firing takes place. This is increased in temperature at a temperature-raising rate of 20° C./minute under a gas pressure of 0.2 Mpa to 2 Mpa in a nitrogen atmosphere, and thus heated to 1800° C. or higher, thereby manufacturing β-sialon phosphors. 
     Inventive examples 1 through 9 involve manufacturing phosphors by varying silicon raw materials, the aluminum raw material and the mixing ratios therebetween, and comparative examples 1 through 3 involve manufacturing phosphors using a silicon raw material without metal silicon. 
     All the phosphors manufactured according to the inventive examples 1 through 9 and the comparative examples 1 through 3 are Eu-activated β-sialon phosphors, and are green light emitting phosphors having a peak wavelength ranging from 520 nm to 560 nm. 
     Inventive Example 1 
     Silicon nitride (Si 3 N 4 ) and metal silicon (Si) were used as a silicon raw material, alumina (Al 2 O 3 ) was used as an aluminum raw material, and europium oxide (Eu 2 O 3 ) was used as an activator. Si 3 N 4  of 4.047 g, Si of 5.671 g, Al 2 O 3  of 0.589 g, and Eu 2 O 3  of 0.141 g were measured and mixed using a mixer and a sieve, and was then filled in a BN crucible and set into a pressure-resistant furnace. In a firing process, heating is carried out up to 500° C. in a vacuum, and an N 2  gas was introduced at 500° C. Under the N 2  atmosphere, the temperature was raised from 500° C. to 1950° C. at 5° C./minute, and firing was performed thereon at 1950° C. under the gas pressure of 0.8 Mpa or higher for five hours. 
     Cooling was performed after the firing process, and the crucible was taken out of the electric furnace. Thereafter, phosphors, generated through the firing at the high temperature, were milled and sieved using a 100-mesh sieve. The phosphors, obtained in the above manner, were washed and dispersed using hydrofluoric acid and hydrochloric acid, were dried sufficiently, and were classified using a 50-mesh sieve, thereby obtaining phosphors of the inventive example 1. 
     Inventive Example 2 
     β-sialon phosphors were manufactured using the same method as in the inventive example 1, except that Si 3 N 4  of 1.349 g and Si of 7.291 g were used. 
     Inventive Example 3 
     β-sialon phosphors were manufactured using the same method as in the inventive example 1, except that Si 3 N 4  of 6.744 g and Si of 4.051 g were used. 
     Inventive Example 4 
     β-sialon phosphors were manufactured using the same method as in the inventive example 1, except that Si 3 N 4  of 9.442 g and Si of 2.430 g were used. 
     Inventive Example 5 
     β-sialon phosphors were manufactured using the same method as in the inventive example 1, except that only Si of 8.101 g, rather than Si 3 N 4 , was used as the silicon raw material. 
     Comparative Example 1 
     β-sialon phosphors were manufactured using the same method as in the inventive example 1, except that only Si 3 N 4  of 13.488 g, rather than Si, was used as the silicon raw material. 
     Inventive Example 6 
     Silicon nitride (Si 3 N 4 ) and metal silicon (Si) were used as a silicon raw material, aluminum nitride (AlN) was used as an aluminum raw material, and europium oxide (Eu 2 O 3 ) was used as an activator. Si 3 N 4  of 5.395 g, Si of 3.241 g, AlN of 0.379 g and Eu 2 O 3  of 0.137 g were measured and mixed using a mixer and a sieve, and were then filled in a BN crucible and set into a pressure-resistant furnace. In a firing process, heating was carried out at 1450° C. for five hours or longer under a nitrogen atmosphere, and cooling was then conducted. Thereafter, the resultant fired material was milled. The milled fired material was filled in the BN crucible again and is set into the pressure-resistant electric furnace. Subsequently, heating was conducted up to 500° C. in a vacuum, and an N 2  gas was introduced at 500° C. Under an N 2  atmosphere, the temperature was raised from 500° C. to 2000° C. at 5° C./minute, and firing was carried out at 2000° C. under the gas pressure of 0.8 Mpa or higher for five hours. 
     Cooling was performed after the firing, and the crucible was taken out of the electric furnace. Thereafter, phosphors, generated through the firing at a high temperature, were milled and sieved using a 100-mesh sieve. The phosphors, obtained in the above manner, were washed and dispersed using hydrofluoric acid and hydrochloric acid, were dried sufficiently, and were classified using a 50-mesh sieve, thereby obtaining phosphors of the inventive example 6. 
     Inventive Example 7 
     β-sialon phosphors were manufactured using the same method as in the inventive example 6, except that Si 3 N 4  of 7.554 g and Si of 1.944 g were used. 
     Inventive Example 8 
     β-sialon phosphors were manufactured using the same method as in the inventive example 6, except that only Si of 6.481 g, rather than Si 3 N 4 , was used as the silicon raw material. 
     Comparative Example 2 
     β-sialon phosphors were manufactured using the same method as in the inventive example 6, except that only Si 3 N 4  of 10.791 g, rather than Si, was used as the silicon raw material. 
     Inventive Example 9 
     β-sialon phosphors were manufactured using the same method as in the inventive example 6, except that Si 3 N 4  of 6.744 g, Si of 4.051 g, Eu 2 O 3  of 0.172 g, and only metal aluminum (Al) of 0.312 g rather than Al 2 O 3  or AlN as the aluminum raw material were used. 
     Comparative Example 3 
     β-sialon phosphors were manufactured using the same method as in the inventive example 9, except that only Si 3 N 4  of 13.488 g rather than Si as the silicon raw material, and Al of 0.473 g were used. 
     The mixing ratios of the raw materials used in the above inventive examples and comparative examples are shown in the following Table 2. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Example 
                   
                   
                 Al 2 O 3   
                   
                   
                   
               
               
                 number 
                 Si3N4 (g) 
                 Si (g) 
                 (g) 
                 AlN (g) 
                 Al (g) 
                 Eu 2 O 3  (g) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Inventive 
                 4.047 
                 5.671 
                 0.589 
                 — 
                 — 
                 0.141 
               
               
                 example 1 
               
               
                 Inventive 
                 1.349 
                 7.291 
                 0.589 
                 — 
                 — 
                 0.141 
               
               
                 example 2 
               
               
                 Inventive 
                 6.744 
                 4.051 
                 0.589 
                 — 
                 — 
                 0.141 
               
               
                 example 3 
               
               
                 Inventive 
                 9.442 
                 2.430 
                 0.589 
                 — 
                 — 
                 0.141 
               
               
                 example 4 
               
               
                 Inventive 
                 — 
                 8.101 
                 0.589 
                 — 
                 — 
                 0.141 
               
               
                 example 5 
               
               
                 Comparative 
                 13.488 
                 — 
                 0.589 
                 — 
                 — 
                 0.141 
               
               
                 example 1 
               
               
                 Inventive 
                 5.395 
                 3.241 
                 — 
                 0.379 
                 — 
                 0.137 
               
               
                 example 6 
               
               
                 Inventive 
                 7.554 
                 1.944 
                 — 
                 0.379 
                 — 
                 0.137 
               
               
                 example 7 
               
               
                 Inventive 
                 — 
                 6.481 
                 — 
                 0.379 
                 — 
                 0.137 
               
               
                 example 8 
               
               
                 Comparative 
                 10.791 
                 — 
                 — 
                 0.379 
                 — 
                 0.137 
               
               
                 example 2 
               
               
                 Inventive 
                 6.744 
                 4.051 
                 — 
                 — 
                 0.312 
                 0.172 
               
               
                 example 9 
               
               
                 Comparative 
                 13.488 
                 — 
                 — 
                 — 
                 0.473 
                 0.172 
               
               
                 example 3 
               
               
                   
               
            
           
         
       
     
     The phosphors, manufactured according to the inventive example 1, were classified by a powder X-ray diffraction (XRD), and the result thereof is shown in  FIG. 115 .  FIG. 115  and JCPD data confirm that the manufactured phosphors are 3-sialon phosphors. 
     Furthermore, the light emission characteristic thereof was measured by emitting excitation light of 460 nm thereto.  FIG. 116  illustrates the light emission spectrums of the β-sialon phosphors obtained using the inventive example 1 and the β-sialon phosphors obtained using the comparative example 1. The β-sialon phosphors obtained using the inventive example 1 are green light emitting phosphors having a peak wavelength of 541 nm and a half amplitude of 54.7 nm. The light intensity thereof is higher than that of the β-sialon phosphors obtained using the comparative example 1 by 27%. 
     The excitation spectrum of the β-sialon phosphors obtained by the inventive example 1 was measured using emission light of 541 nm as detection light. The result thereof is shown in  FIG. 117 . It can be seen that an excitation band exists in an ultraviolet light region and even a visible light region of about 500 nm. 
     β-sialon phosphors of 7 wt %, obtained by each of the inventive examples 1 to 9 and comparative examples 1 to 3, red CaAlSiN 3 : Eu phosphors of 3 wt %, and silicon resin of 10 wt % were appropriately mixed and made into a slurry. This slurry is injected into a cup on a mount lead equipped with a blue LED, and is then cured at 130° C. for an hour. Using the resultant phosphors, a white LED was manufactured. The light intensity of the manufactured white LED was measured. 
     The peak wavelengths of light, emitted from the β-sialon phosphors, obtained using the inventive examples 1 to 9 and the comparative examples 1 to 3, and the light intensity of white LEDs using the same are shown in Table 3 below (wt %). 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                   
                   
                   
                 Peak 
                   
               
               
                   
                 silicon  
                   
                 wave- 
                   
               
               
                   
                 raw  
                 Aluminum 
                 length 
                   
               
               
                   
                 material 
                 raw  
                 (nm) of  
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Example 
                   
                 Si/Si 3 N 4   
                 material 
                 emitted 
                 Intensity 
               
               
                 number 
                 Kinds 
                 (wt%) 
                 Kinds 
                 light 
                 (sb) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Inventive 
                 Si/Si 3 N 4   
                 70/30 
                 Al 2 O 3   
                 541 
                 127 
               
               
                 example 1 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si/Si 3 N 4   
                 90/10 
                 Al 2 O 3   
                 541 
                 124 
               
               
                 example 2 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si/Si 3 N 4   
                 50/50 
                 Al 2 O 3   
                 541 
                 124 
               
               
                 example 3 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si/Si 3 N 4   
                 30/70 
                 Al 2 O 3   
                 541 
                 107 
               
               
                 example 4 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si 
                 — 
                 Al 2 O 3   
                 541 
                 118 
               
               
                 example 5 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 Si 3 N 4   
                 — 
                 Al 2 O 3   
                 541 
                 100 
               
               
                 example 1 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si/Si 3 N 4   
                 50/50 
                 AIN 
                 540 
                 113 
               
               
                 example 6 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si/Si 3 N 4   
                 30/70 
                 AIN 
                 538 
                 115 
               
               
                 example 7 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si 
                 — 
                 AIN 
                 540 
                 106 
               
               
                 example 8 
                   
                   
                   
                   
                   
               
               
                 Comparativc 
                 Si 3 N 4   
                 — 
                 AIN 
                 540 
                 100 
               
               
                 example 2 
                   
                   
                   
                   
                   
               
               
                 Inventive 
                 Si/Si 3 N 4   
                 50/50 
                 Al 
                 540 
                 119 
               
               
                 example 9 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 Si 3 N 4   
                 — 
                 AIN 
                 536 
                 100 
               
               
                 example 3 
                   
                   
                   
                   
                   
               
               
                   
               
            
           
         
       
     
     The phosphors, obtained using the inventive examples 1 to 9 and the comparative examples 1 to 3, emit light having a peak wavelength of about 540 nm, and are thus determined to be green light emitting phosphors. The white LEDs using the phosphors, obtained using the inventive examples 1 to 3, have relatively high light intensity levels ranging from 124 to 127. 
     However, the inventive example 4 in which the content of metal silicon is smaller than the content of silicon nitride, realizes a lower light intensity level than the light intensity levels in the inventive examples 1 to 3 in which the content of the metal silicon is greater than the content of silicon nitride. The inventive examples 5 and 8, utilizing only Si as the silicon raw material, realize a lower light intensity level than the light intensity levels in the inventive examples 1, 2, 3 and 6, while realizing a higher light intensity level than the light intensity levels of the inventive examples 4, 6 and 7, in which the content of metal silicon is smaller than the content of silicon nitride. Thus, it can be confirmed that β-sialon phosphors realizing high light intensity can be manufactured when using the metal silicon. 
     The comparative examples 1 through 3 using only Si 3 N 4  as the silicon raw material each realize a light intensity level of 100. Thus, it can be seen that they have lower light intensity levels than when metal silicon is not used as a base raw material as in the inventive examples. 
     In addition, a high level of light intensity is attained even when both metal silicon and metal aluminum are used as in the inventive example 9. 
     The above-described β-sialon phosphors may be advantageously applied to light emitting devices and modules that generate white light by the combination with other phosphors. 
     Backlight Unit 
     A backlight unit, according to the present invention, includes the above-described light emitting device package. The light emitting device package, equipped with the semiconductor light emitting device according to the present invention, may be used as light sources for various devices such as lighting equipment, car headlights and the like, as well as surface light sources such as backlight units. 
     Hereinafter, a backlight unit including the light emitting device package will be described according to various embodiments of the present invention. 
       FIGS. 118A and 118B  are schematic views illustrating a surface light source device including a flat light guide plate, i.e., a backlight unit, according to an exemplary embodiment of the present invention. 
     As shown in  FIG. 118A , a backlight unit  5000  including a flat light guide plate according to the present invention, is a tandem surface light source device, and includes N LED light source modules  5010 , and N flat light guide plates  5020 . 
     Each of the N LED light source modules  5010  includes a board  5011 , and a plurality of light emitting device packages  5012  arranged in a row on the board  5011 . The N LED light source modules  5010 , configured in the above manner, are arranged parallel to one another. Each flat light guide plate  5020  is arranged and installed along one side of a corresponding LED light source module of the N LED light source modules  5010 . 
     The backlight unit having the flat light guide plates  5020  may include a reflective member (not shown) disposed under the LED light source module  5010  and the flat light guide plate  5020  and reflecting light emitted from the LED light source module  5010 . 
     Also, an optical sheet (not shown) may be provided on the flat light guide plate  5020 . An example of the optical sheet may include a diffusion sheet diffusing light, output toward a liquid crystal panel after being reflected by the reflective member and refracted by the flat light guide plate, in various directions, or a prism sheet collecting light, having passed through the diffusion sheet, within a front viewing angle. 
     In more detail, the LED light source module  5010  may include a plurality of light emitting device packages  5012  each mounted using a top-view method. The flat light guide plate  5020  is a plate-type, and is formed of a transparent material to transmit light and disposed in a direction in which light is emitted from the LED light source. The flat light guide plate is simple in shape and easy to manufacture as compared to a wedge type light guide plate, and facilitates the positioning thereof on an LED light source. 
     The flat light guide plate  5020  includes a light input portion  5021  receiving light emitted from the LED light source module  5010 , a light output portion  5024  having a flat plate shape with a uniform thickness and outputting light, received from the LED light source module, toward a liquid crystal panel as illuminating light, and a leading edge portion  5022  protruding from the opposite side to the light input portion  5021  with reference to the light output portion  5024 , and having a smaller thickness than that of the light input portion  5021 . The flat light guide plate  5020  is disposed such that the leading edge portion  5022  thereof covers the LED light source module  5010 . Namely, the N+1 th  LED light source module  5010  is placed under the leading edge portion  5022  of the n th  flat light guide plate  5020 . The bottom of the leading edge portion  5022  of the flat light guide plate  5020  has a prism shape  5023 . 
     As shown in  FIG. 118B , light emitted from the light emitting device package  5012  is not directly output to the flat light guide plate  5020  but is scattered and dispersed by the prism, shape  5023  formed on the bottom of the leading edge portion  5022  of the flat light guide plate  5020 . Accordingly, hot spots may be removed from the light guide plate over the LED light source module  5010 . 
       FIG. 119  is a schematic perspective view illustrating the flat light guide plate  5020  depicted in  FIGS. 118A and 118B . As shown in  FIG. 119 , the flat light guide plate  5020  includes the light input portion  5021  receiving light emitted from the light source module  5010  including the plurality of light emitting device packages  5012 , the light output portion  5024  having a flat plate shape with a uniform thickness and outputting light, incident on the light input portion  5021 , toward a liquid crystal panel (not shown) as illuminating light, and the leading edge portion  5022  formed at the opposite side to the light input portion  5021  with reference to the light output portion  5024  and having a smaller section than the light incidence section of the light input portion  5021 . 
     The leading edge portion  5022  has the prism shape  5023  in order to disperse a portion of light emitted from the light emitting device packages  5012  arranged thereunder. The prism shape may be at least one of a triangular prism, a cone prism and a hemispherical prism. 
     The prism shape of the leading edge portion  5022  may be formed on the entirety of the leading edge portion  5022 , or may be formed only over the light emitting device packages  5012 . The prism shape is contributive to removing hot spots generated on the flat light guide plate  5020  over the light emitting device packages  5012 . 
     According to the present invention, the prism shape  5023  is formed on the bottom of the leading edge portion  5022  of the flat light guide plate  5020 . Thus, there is no need for performing the process of forming a separate diffusion sheet and a prism sheet between the light emitting device package  5012  and the flat light guide plate  5020  in order to disperse hot spots that are generated by a portion of the light, emitted from the light emitting device package  5012 , over the flat light guide plate  5020 . 
     A backlight unit including a flat light guide plate, according to another exemplary embodiment of the present invention, will now be described with reference to  FIGS. 120 through 125 . 
       FIG. 120  is an exploded perspective view illustrating a backlight unit according to another exemplary embodiment of the present invention,  FIG. 121  is a cross-sectional view taken along line I-I′ of  FIG. 120 , illustrating the assembled backlight unit. Here, the backlight unit may include a plurality of light guide plates. However, two light guide plates are illustrated for the ease of description. 
     Referring to  FIGS. 120 and 121 , a backlight unit  600  includes a lower cover  6010 , a light guide plate  6020 , a light source device  6030  and a fixing member  6040 . 
     The lower cover  6010  has a receiving space. For example, the receiving space may be formed by a plate constituting the bottom of the lower cover  6010 , and the sidewall extending from the edge of the plate in a perpendicular manner. 
     The lower cover  6010  may include a coupling hole or a coupling portion  6011  to which the fixing member  6040  to be described later is coupled. Here, the coupling hole or the coupling portion  6011  may be provided in the form of a hole portion through which the fixing member  6040  penetrates, or a recess portion in which the fixing member  6040  is inserted. 
     The light guide plate  6020  may be provided in the form of a plurality of divided light guide plates  6020 . The divided light guide plates  6020  are disposed in the receiving space of the lower cover  6010  in a parallel manner. 
     Each of the light guide plates  6020  has through holes  6021  penetrating the body thereof. The through hole  6021  is disposed at the edge of the light guide plate  6020 . In this embodiment of the present invention, the location and number of through holes  6021  is not limited. The through hole  6021  is located corresponding to the coupling portion  6011 . 
     Although illustrated as having a quadrangular shape, the light guide plate  6020  is not limited to the illustrated shape, but may have various shapes such as a triangle, a hexagon or the like. 
     A plurality of light source devices  6030  are disposed at one side of each light guide plate  6020  to provide light to the light guide plate  6020 . Each of the light source devices  6030  may include a light emitting device package  6031 , a light source that forms light, and a board  6032  including a plurality of circuit patterns for supplying the driving voltage of the light emitting device package  6031 . 
     For example, the light emitting device package  603  may include sub-light emitting devices respectively realizing blue, green and red colors. Red light, green light and red light emitted from the sub-light emitting devices, realizing blue, green and red colors respectively, are mixed to generate white light. Alternatively, the light emitting device package may include a blue light emitting device and phosphors that convert blue light from the blue light emitting device into yellow light. At this time, the blue light and the yellow light are mixed to thereby realize white light. 
     The light emitting device package and the phosphors have already been described above in detail, and thus a description thereof will be omitted. 
     Light formed by the light source device  6030  is incident on the side surface of the light guide plate  6020  and is output upwardly by the total internal reflection of the light guide plate  6020 . 
     The fixing member  6040  serves to fix the light guide plate  6020  to the lower cover  6010  so as to prevent the movement of the light guide plate  6020 . The fixing member  6040  is inserted into the through hole  6021  of the light guide plate  5020  to thereby fix the light guide plate  6020  onto the lower cover  6010 . Furthermore, the fixing member  6040  may be coupled with the coupling portion  6011  by way of the through hole  6021  of the light guide plate  120 . For example, the fixing member  6040  may pass through the coupling portion  6011  configured as the hole portion or be inserted into the coupling portion  6011  configured as the recess portion. 
     The fixing member  6040  includes a body portion  6042 , and a head portion  6041  extending from the body portion  6042 . 
     The body portion  6042  penetrates the through hole of the light guide plate  6020 , and is coupled with the coupling portion  6011 . That is, the body portion  6042  couples the light guide plate  6020  and the lower cover  6010  with each other to thereby fix the light guide plate  6020  on the lower cover  6010 . 
     The head portion  6041  has a wider width than the body portion  6042  to thereby prevent the fixing member  6040  from being completely separated from the through hole  6021  of the light guide plate  6020 . 
     The head portion  6041  may have one of various sectional shapes such as semi-circular, semi-oval, quadrangular and triangular shapes. Here, the head portion  6041 , when having a triangular sectional shape, may minimize contact between the fixing member  6040  and an optical member  6060  to be described later, and this may minimize the generation of black spots caused by the fixing member  6040 . 
     The light guide plate  6020  and the optical member  6060  are spaced apart from each other at a predetermined interval, and thus light emitted from the light guide plate  6020  may be uniformly provided on the optical member  6060 . Here, the head portion  6041  supports the optical member  6060  and serves to maintain the interval between the light guide plate  6020  and the optical member  6060 . Here, the interval between the light guide plate  6020  and the optical member  6060  may be adjusted by controlling the height of the head portion  6041 . 
     The fixing member  6040  may be formed of a light transmissive material, for example transparent plastic, in order to minimize its influence on image quality. 
     Furthermore, a reflective member  6050  may be disposed under each of the light guide plates  6020 . The reflective member  6050  reflects light emitted to the lower side of the light guide plate  6020  and thus causes the light to be re-incident on the light guide plate  6020 , thereby enhancing the light efficiency of the backlight unit. 
     The reflective member  6050  may include a through portion  6051  corresponding to the through hole  6021  and the coupling portion  6011 . The fixing member  6040  may be coupled with the coupling portion  6011  by way of the through hole  6021  and the through portion  6051 . Accordingly, when the reflective member  6050  is provided in the form of a plurality of divided reflective members  6050  like the light guide plate  6020 , the reflective member  6050  can be fixed on the lower cover  6010  by the fixing member  6040 . 
     Furthermore, the backlight unit may further include the optical member  6060  disposed over the light guide plate  6020 . An example of the optical member  6060  may include a diffusion plate, a diffusion sheet, a prism sheet and a protective sheet disposed over the light guide plate  6020 . 
     Thus, according to this embodiment of the present invention, the backlight unit includes a plurality of divided light guide plates, thereby further enhancing a local dimming effect through local driving. 
     Also, the plurality of divided light guide plates are fixed on the lower cover using the fixing member, thereby preventing defects caused by the movement of the light guide plate. 
     Moreover, since the fixing member can maintain the uniform interval between the light guide plate and the optical member, light can be uniformly provided to a liquid crystal panel. 
       FIG. 122  is a plan view illustrating an LED backlight unit according to another exemplary embodiment of the present invention.  FIG. 123  is a cross-sectional perspective view illustrating region A indicated in  FIG. 122  before a board is coupled, and  FIG. 124  is a cross-sectional perspective view illustrating the region A indicated in  FIG. 122  after the board is coupled.  FIG. 125  is a cross-sectional view taken along line II-II′ of  FIG. 124 . 
     As shown in  FIGS. 122 through 125 , an LED backlight unit, according to the present invention, includes a lower cover  6110 , a plurality of light guide plates  6120 , a board  6131 , a plurality of LED packages  6132 , and a fixing member  6140 . The lower cover  6110  has a coupling hole or portion provided in the form of a first through hole  6110   a  or a recess. The plurality of light guide plates  6120  are disposed on the lower cover  6110 . The board  6131  is disposed at one side of each of the light guide plates  6120  in a manner parallel to the bottom of the bottom of the lower cover  6110 , includes wires receiving voltage from the outside, and has a second through hole  6131   a  corresponding (or facing) the first through hole  6110   a  of the lower cover  6110 . The plurality of light emitting device packages  6132  are mounted on the board  6131  provided at one side of a corresponding light guide plate of the light guide plates  6120 . The fixing member  6140  is coupled with the second through hole  6131   a  of the board  6131  and/or the first through hole  6110   a  of the lower cover  6110 , and press the edge portions of the adjacent light guide plates  6120 . 
     Here, the lower cover  6110  has the first through hole  6110   a  penetrating a plate in the form of, for example, a circular, rectangular or oval shape (alternatively, a coupling recess recessed in the plate). Here, the plate serves as the bottom of the receiving space of the lower cover  6110 . Such a lower cover  6110  is formed of material such as iron (Fe) or electrolytic galvanized iron (EGI). Also, the lower cover  6110  may have a sidewall, namely, a side frame extending upwardly from the edge of the plate, serving as the bottom, in a perpendicular manner. The bottom of the lower frame may be divided into a plurality of regions arranged in a row in order to realize a backlight unit capable of local dimming. The plurality of regions may be bordered by a recess or the like. Of course, the recess, bordering the plurality of regions, corresponds to a receiving recess for the board  6131  as will be described later. 
     The first through hole  6110   a  in the lower cover  6110  may have various shapes besides a circular, oval or rectangular shape. However, the first through hole  6110   a  may have two parallel longer sides and two shorter sides formed with a predetermined curvature at both ends of the two longer sides so as to connect the two longer sides. Here, the first through hole  6110   a  may be formed such that the longer axis (Y-axis) of the first through hole  6110   a  is located in the same direction as the direction in which light moves. Even when the coupling recess, rather than the first through hole  6110   a , is formed, the coupling recess has the same structural characteristic as described above. 
     A reflective plate (not shown) is attached to the entirety of the bottom of the lower cover  6110 . Alternatively, when a receiving recess is formed in the bottom of the lower cover  6100 , a plurality of reflective plates (not shown) are respectively attached on a plurality of bottom regions other than the receiving recess. The reflective plate utilizes a white polyester film or a film coated with metal such as Ag or Al. The visible light reflectance of the reflective plate ranges from about 90% to 97%. The thicker the coated film is, the higher the reflectance becomes. 
     The plurality of reflective plates on the bottom of the lower cover  6110  may each extend so as to be placed between the light emitting device packages  6132  providing light and the light guide plate  6120  adjacent to the back of the light emitting device package  6132 . In this case, induced light provided from one side of the light guide plate  6120  may be reflected again by the reflective plate without being interrupted by the light emitting device package  6132  disposed at the opposite side of the light guide plate  6120 . Then, the reflected light may be provided toward an optical member (not shown) provided at the upper side, thereby enhancing the light reflection efficiency. 
     An LED light source  6130  is provided in the receiving recess of the lower cover  6110  or at one side of the light guide plate  6120 . The LED light source  6130  includes the board  6131 , i.e., a printed circuit board (PCB), and the light emitting device package  6132  mounted on the board  6131 . The board  6131  is provided in, for example, the receiving recess to thus be placed on the same horizontal level as the bottom of the lower cover  6110 , includes wires for receiving voltage from the outside, and has a second through hole  6131   a  corresponding to the first through hole  6110   a  of the lower cover  6110 . 
     The board  6131  has the second through hole  6131   a  formed between the light emitting device package  6132  and the light emitting device package  6132 . The board  6131  having the second through hole  6131   a  is provided on the bottom of the lower cover  6110  such that the second through hole  6131   a  corresponds to (or faces) the first through hole  6110   a  of the lower cover  6110 . The second through hole  6131   a  in the board  6131  may have, for example, a circular or oval shape like the first through hole  6110   a  of the lower cover  6110 . However, according to the present invention, the second through hole  6131   a  may have two parallel longer sides and two shorter sides formed with a predetermined curvature at both ends of the two longer sides so as to connect the two longer sides. At this time, the second through hole  6131   a  is formed such that the direction of the longer axis (X-axis) of the second through hole  6131   a  becomes perpendicular to the direction in which light moves. Accordingly, the second through hole  6131   a  of the board  6131  has its longer axis (X-axis) crossing the longer axis (Y-axis) of the first through hole  6110   a  of the lower cover  6110 . 
     The size of the second through hole  6131   a  formed in the board  6131 , more precisely, the interval between the two longer sides thereof, may be associated with the diameter of the body of the fixing member  6140  including a screw thread. This is because the size of the second through hole  6131   a  may affect the interval between the light emitting device package  6132  providing light and the light guide plate  6120  receiving and inducing light provided from the light emitting device package  6132 . This will be described later. 
     In addition, the light emitting device package  6132  includes a package body  6133  fixed on the board  6131 , forming an exterior frame and having a receiving recess, a light emitting device  6136  mounted in the receiving recess of the package body  6133  and providing light, and a pair of first and second electrode structures (not shown) exposed in the receiving recess, electrically connected with a wire formed on the board  6131 , and on which the light emitting device  6135  is mounted. 
     In the case that the light emitting device  6136  is a blue light emitting device, the light emitting device package  6132  may additionally include a resin encapsulant  6136  in the receiving recess in order to provide white light. Here, the resin encapsulant  6136  may include yellow phosphors. For example, the resin encapsulant  6136  may be formed by injecting a gel-phase epoxy resin containing YAG-based yellow phosphors or a gel-phase silicon resin containing YAG-based yellow phosphors into the receiving recess of the package body  6133 , and subsequently performing UV curing or thermal curing thereon. 
     Of course, the present invention is not limited to the light emitting device package  6132  including the blue light emitting device and the yellow phosphors. For example, the light emitting device package  6132  may include a near ultraviolet chip and a resin encapsulant provided on the near ultraviolet chip and containing a mixture of red, green and blue phosphors. Also, the resin encapsulant may be formed by sequentially stacking layers respectively containing red, green and blue phosphors. 
     The plurality of light guide plates  6120  are provided on the bottom of the lower cover  6110  divided into a plurality of regions, respectively. In this case, the side surface of the light guide plate  6120  may be adhered to the package body  6133 , so that light, provided from the light emitting device  6135  mounted in the receiving recess of the package body  6133 , can be induced into the light guide plate  6120  without loss. 
     The light guide plate  6120  is formed of PMMA, and as PMMA has the lowest light absorbency in a visible light region among polymer materials, it thus has significantly high transparency and gloss. The light guide plate  6120 , formed of PMMA, is not broken or deformed due to its high mechanical strength, and has high visible-light transmittance of 90% to 91% and considerably low internal loss. Also, this light guide plate  6120  has superior chemical properties, resistance and mechanical properties such as tensile strength and bending strength. 
     The fixing unit  6140  is coupled to the board  6131  between the light guide plates  6120 . The fixing member  6140  is formed of a transparent material and has a screw-like shape. The fixing member  6140  is coupled by penetrating the second through hole  6131   a  of the board  6131  and the first through hole  6110   a  of the lower cover  6110  corresponding to the second through hole  6131 . Thus, the fixing member  6140  fixes the adjacent light guide plates  6120  placed at both sides of the light emitting device package  6132 , that is, at the front side outputting light and the back side opposite to the front side, while maintaining a uniform interval between the light guide plates. 
     Here, the fixing member  6140 , according to the present invention, is formed of a transparent material, so that light, induced in the light guide plate  6120 , can be provided to the optical member above without interruption. The fixing member  6140  may be formed of the same material as the light guide plate  6120 . 
     The fixing member  6140 , according to the present invention, includes a head portion that may have various shapes such as a circular or quadrangular shape, and a body portion extending from the head portion and having a cylindrical shape or the like. The fixing member  6140  may be fixed to the second through hole  6131   a  of the board  6131  and/or the first through hole  6110   a  of the lower cover  6110  by using a screw thread formed on the outer surface of the body portion of the fixing member  6140 . Of course, the body portion of the fixing member  6140  may have a square column shape. 
     The head portion has a size large enough to cover the interval between the light guide plates  6120 , and the edge of the light guide plates  6120  in part. Thus, the size of the head portion may be slightly varied depending on the interval between the light guide plates  6120 , and the diameter of the body portion may be the same as the interval between the two parallel longer sides of the second through hole  6131   a  of the board  6131  and/or the first through hole  6110   a  of the lower cover  6110 . 
     Furthermore, the size of the head portion of the fixing unit  6140  or the diameter of the body portion thereof may be slightly varied depending on the size of the second through hole  6131   a  of the board  6131  described above. For example, when the size of the second through hole  6131   a  of the board  6131  is small, the diameter of the body portion of the fixing member  6140  is also small. This may mean that the interval between the light emitting device package  6132  and the light guide plate  6120  can be reduced. 
     When the fixing member  6140  is coupled with the board  6131  and/or the lower cover  6110  in a screw-like manner, the head portion of the fixing member  6140  presses the upper edge portions of the adjacent light guide plates  6120  disposed on the board  6131  to which the light emitting device package  6132  is fixed. Accordingly, the movements of the light guide plates  6120  can be prevented even under external shock. 
     Also, a nut may be coupled to a portion of the fixing member  6140  exposed to the outside through the first through hole  6110   a  of the lower cover  6110 , so that the fixing member  6140  can attain reinforced strength. 
     Consequently, the fixing member  6140  coupled on the board  6131  may serve as a spacer between the light emitting device package  6132  and the light guide plate  6120 . Thus, the fixing member  6140  maintains a uniform interval between the light emitting device package  6132  and the light guide plate  6120 , thereby becoming capable of coping with the shrinkage and/or expansion of the light guide plate  6120 . 
     Of course, the fixing member  6140  is not limited to having a screw thread. For example, as shown in  FIG. 121 , the fixing member  6140  may be provided as a screw having a head portion and an opposite hooked end portion. In this case, the fixing member  6140  penetrates the second through hole  6131   a  of the board  6131  and the first through hole  6110   a  of the lower cover, and is fixed to the lower cover  6110  by the hooked end portion. 
     An optical member (not shown) is provided above the plurality of light guide plates in order to supplement the optical characteristic of light provided through the light guide plates  6120 . Here, the optical member may include a diffusion plate having a diffusion pattern to reduce the non-uniformity of light transmitted through the light guide plates  6120 , and a prism sheet having a condensing pattern for enhancing the front intensity of light. 
     By the above construction according to the present invention, the fixing member  6410  is provided between the light guide plates  6120  so as to fix the light guide plates  6120  while maintaining a uniform interval therebetween. This construction can prevent the movement of the light guide plates  6120 , caused by external shock, and cope with the shrinkage of the light guide plates  6120  in a direction (X-axis) perpendicular to the direction in which light moves. 
     The second through hole  6131   a  of the board  6131 , having a longer axis and a shorter-axis direction, can deal with the shrinkage of the board  6131  in the longer-axis direction (X-axis) of the second through hole  6131   a.    
     Furthermore, the fixing member  6140  is coupled with the first through hole  6110   a  having a longer-axis (Y-axis) in the direction that light moves. Thus, even if the light guide plate  6120  shrinks and/or expands, the light guide plate  6120 , the fixing member  6140  and/or the board  6131  can move together along the longer axis (Y-axis) of the first through hole  6110   a  of the lower cover  6110 . Accordingly, the uniform interval between the light guide plate  6120  and the light emitting device package  6132  can be maintained, bright spots and bright lines can be further prevented as compared to the related art. 
     A liquid crystal display according to the present invention may include the LED backlight unit according to the above exemplary embodiments, and may further include a liquid crystal panel (not shown) provided on the optical member. 
     Here, the liquid crystal display may further include a mold structure called a main support in order to prevent the warp of the display device caused by external shock. The backlight unit is provided under the main support, and the liquid crystal panel is loaded on the main support. 
     The liquid crystal panel includes a thin film transistor array substrate and a color filter substrate that are attached together, and a liquid crystal layer injected between these two substrates. 
     Signal lines such as gate lines and data lines cross one another on the thin film transistor array substrate, and thin film transistors (TFT) are formed at the respective crossings of the data and gate lines. The TFT transfers video signals, which are to be sent to liquid crystal cells of the liquid crystal layer from the data lines, that is, red (R), green (G) and blue (B) data signals, in response to scan signals provided through the gate lines. Also, pixel electrodes are formed in the pixel regions between the data and gate lines. 
     The color filter substrate includes thereon, a black matrix formed corresponding to the gate and data lines of the thin film transistor array substrate, color filters formed in regions defined by the black matrix to provide red (R), green (G) and blue (B) colors, and a common electrode provided on the black matrix and the color filters. 
     Data pads extending from the data lines and gate pads extending from the gate lines are formed at the edge of the thin film transistor array substrate attached with the color filter substrate. A gate driver and a data driver are respectively connected to the data pads and the gate pads, and supply signals thereto. 
     An upper cover may be provided on the liquid crystal panel. Here, the upper cover covers the four sides of the liquid crystal panel and is fixed to the lower cover  210  or the sidewall of the main support. Of course, the upper cover is formed of the same material as the lower cover  210 . 
     As set forth above, according to exemplary embodiments of the invention, the semiconductor light emitting device includes a first electrode having a portion formed on a light-emitting surface and the other portion disposed under an active layer, thereby maximizing the light-emitting area. 
     Since the electrode is uniformly disposed on the light emitting surface, the current can be spread stably even when high operating current is applied thereto. 
     Furthermore, the uniform current spreading can be achieved to thereby reduce current crowding during high-current operation and thus enhance reliability. 
     While the present invention has been shown and described in connection with the exemplary embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.