Abstract:
A compound semiconductor light emitting device for preparing a chip which improves the light extraction efficiency, enables mounting of easy positioning with only once wire bonding, and leads to a reduction in the manhour. One face of an insulative substrate ( 11 ) is overlaid with a semiconductor layer ( 4 ) consisting of a plurality of semiconductor thin films to form an active layer ( 15 ). One electrode ( 33 ) is formed on the top face of this semiconductor layer ( 4 ), and the other electrode ( 33 ) on the other face of the insulative substrate ( 11 ). For the exposure of a first semiconductor thin film layer ( 13 ) connected to the other electrode ( 33 ), the semiconductor film over the first semiconductor thin film layer ( 13 ) is removed to form an exposure region ( 10 ). This exposure region ( 10 ) is provided with a through hole ( 2 ) penetrating through the insulative substrate ( 11 ) and first semiconductor thin film layer ( 13 ).  
     The first semiconductor thin film layer ( 13 ) and the other electrode ( 33 ) are electrically connected with a conductive material ( 3 ) formed on the through hole ( 2 ).

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a compound semiconductor light emitting device such as a blue light emitting diode and a blue laser diode as well as its manufacturing method. This invention particularly relates to a light emitting device comprising a nitride-based compound semiconductor epitaxially grown on an insulative substrate such as a sapphire substrate, and its manufacturing method.  
         [0003]     2. Description of Prior Art  
         [0004]     Epitaxial growth of nitride-based compound semiconductors used for blue light emitting diodes, blue laser diodes and the like is generally performed on a sapphire (Al 2 O 3 ) substrate whose lattice constant is similar to that of the nitride-based compound semiconductors.  FIG. 23  illustrates an example of a basic structure of a blue light emitting semiconductor device comprised of a nitride-based compound semiconductor. A buffer layer  220  made of Al x Ga 1-x N (0≦X≦1) for example is formed on a sapphire substrate  210 , and an n-type contact layer  230  made of n-type GaN doped with silicon (Si) for example is formed on the buffer layer  220 . An n-type cladding layer  240  made of n-type Al x Ga 1-x N (0≦X≦1) doped with silicon (Si) for example is formed on the n-type contact layer  230 . A multi-quantum well structure active layer  250  having a composition of Al a In b Ga 1-a-b N ( 0 ≦a, 0≦b, a+b≦1) for example is formed on the n-type cladding layer  240 . On this active layer  250 , a p-type cladding layer  260  made of p-type Al y Ga 1-y N (0≦Y≦1)doped with magnesium (Mg) for example is formed, and a p-type contact layer  270  made of p-type GaN doped with magnesium (Mg) is formed on the p-type cladding layer  260 .  
         [0005]     A p-type electrode  280  is provided on a surface of the p-type contact layer  270 . A part of the laminated semiconductor layer is etched to expose the n-type contact layer  230 , on which an n-type electrode  290  is provided.  
         [0006]     Electric current does not pass between the electrodes when the electrodes are respectively provided on a rear surface of the substrate and a front surface of the semiconductor layer to bring a pair of electrodes like a conventional light emitting device comprising a conductive substrate because the sapphire substrate behaves as an insulator.  
         [0007]     Therefore, as described above, a part of the semiconductor layer is removed from its front surface so that a semiconductor layer of one conductivity type is exposed and an electrode of the other conductivity type is formed on the remaining front surface. Thus, the nitride-based compound semiconductor light emitting device delivers performance by conducting electricity through a pair of electrodes, both of which are provided on the front surface side of the semiconductor layer.  
         [0008]     With this structure, the light extraction efficiency is low since the pair of electrodes existing on one side of the semiconductor device shade a lot of light. Also the pair of electrodes existing on one side of the semiconductor device require wire-bonding at least twice. When a chip is mounted face down on a board, the electrodes on the chip must be accurately aligned with corresponding electrodes on the base, involving difficulty in precise alignment.  
         [0009]     By the way a semiconductor light emitting device comprising a sapphire substrate with a contact hole to make contact with a semiconductor layer from the sapphire substrate side is disclosed in JP173235/1998, A. This semiconductor light emitting device comprises a sapphire substrate, wherein a rear side thereof is terraced, and a contact hole is provided to a thin-walled part of the terraced rear side of the substrate by reactive ion etching so as to make a semiconductor layer exposed.  
         [0010]     It is surely possible to contact the semiconductor layer from the sapphire substrate side, and the electrodes are separately disposed on the substrate side and the semiconductor layer side in the semiconductor light emitting device disclosed in the above-mentioned specification.  
         [0011]     However, the manufacturing process of this device becomes complicated because the substrate must be terraced in advance to form the contact hole by reactive ion etching, which may cause frequent cracks in the substrate.  
         [0012]     One of the objectives of the present invention is to improve the light extraction efficiency. Another objective is to provide a chip which enables mounting of easy positioning with only once wire bonding, and leads to a reduction in the manhour. A further objective of the present invention is to provide a device with reduced numbers of manufacturing processes and increased process yield by reducing occurrence of cracks in substrates.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention is characterized by a compound semiconductor light emitting device comprising an insulative substrate, a semiconductor layer including a plurality of semiconductor thin films laminated on one surface of the insulative substrate to form an active layer, one electrode provided on top surface of the semiconductor layer, the other electrode provided on the other surface of the insulative substrate, an exposure region formed by removing semiconductor films on a first semiconductor thin film layer so that the first semiconductor thin film layer to be connected to the other electrode is exposed, a through hole formed in the exposure region so as to penetrate the insulative substrate and the first semiconductor thin film layer, and an electrical path formed in the through hole to electrically connect the first semiconductor thin film layer and the other electrode, as recited in claim  1 .  
         [0014]     Also, the present invention is characterized by that the electrical path is comprised of either a conductive material formed on a wall inside the through hole or a conductive material filled in the through hole, as recited in claim  2 .  
         [0015]     Additionally, the present invention is characterized by that the electrode for the electrical path provided on the other surface of the insulative substrate comprises a pad electrode for wire bonding, as recited in claim  3 .  
         [0016]     The present invention is further characterized by that the insulative substrate is a sapphire substrate, and the semiconductor thin film layer is a gallium nitride compound semiconductor layer, as recited in claim  4 .  
         [0017]     Additionally, the present invention is characterized by that the one electrode is electrically connected to a base, and light is extracted mainly from the insulative substrate side, as recited in claim  5 .  
         [0018]     The present invention is also characterized by that a diameter of the through hole ranges from 30 μm to 100 μm, as recited in claim  6 .  
         [0019]     The present invention is characterized by that a groove or a longitudinal hole in addition to the through hole is formed in the insulative substrate so that the electrode provided on the other surface of the insulative substrate and the first semiconductor thin film layer are electrically connected through an electrical path in addition to the electrical path, as recited in claim  7 .  
         [0020]     The present invention is characterized by a manufacturing method of a compound semiconductor light emitting device comprising laminating a plurality of semiconductor thin films to form a semiconductor layer on one surface of an insulative substrate in order to form an active layer, and providing one electrode on top surface of the semiconductor layer, and the method further comprising forming an exposure region by removing semiconductor films on a first semiconductor layer so that a first semiconductor thin film layer to be contacted with the other electrode is exposed, forming a through hole in the exposure region so as to penetrate the insulative substrate and the first semiconductor layer by laser-processing, and electrically connecting the electrode provided on the other surface of the insulative substrate and the first semiconductor thin film layer through an electrical path formed in the through hole, as recited in claim  8 .  
         [0021]     Also, the present invention is characterized by that the through hole penetrating the device is formed in the exposure region by irradiating a laser from the laminated semiconductor layer side, as recited in claim  9 .  
         [0022]     Additionally, the present invention is characterized by that an inside of the through hole is cleaned by dry etching after the through hole is formed, as recited in claim  10 .  
         [0023]     The present invention is further characterized by that an inside of the through hole is cleaned by dry etching using chloride or fluoride gas after the through hole is formed, as recited in claim  11 .  
         [0024]     The present invention is characterized by that a wafer including a plurality of the light emitting devices is divided into individual light emitting devices along grooves formed by laser-processing, as recited in claim  12 .  
         [0025]     The present invention is characterized by that semiconductor layers damaged by laser-processing are removed by dry etching using chloride or fluoride gas after the grooves are formed, as recited in claim  13 .  
         [0026]     The present invention is further characterized by that laser-processing for forming the grooves is performed from the insulative substrate side, or from the laminated semiconductor layer side, or from both the insulative substrate side and the laminated semiconductor layer side, as recited in claim  14 .  
         [0027]     The present invention is characterized by a compound semiconductor light emitting device comprising an insulative substrate, a semiconductor layer including a plurality of semiconductor thin films laminated on one surface of the insulative substrate to form an active layer, one electrode provided on top surface of the semiconductor layer, the other electrode provided on the other surface of the insulative substrate, a longitudinal hole formed by laser-processing, the hole penetrating the insulative substrate and having a depth reaching a first semiconductor thin film layer to be connected to the other electrode, and an electrical path made of a conductive material formed in the longitudinal hole to electrically connect the first semiconductor thin film layer and the other electrode, as recited in claim  15 .  
         [0028]     Also, the present invention is characterized by that the conductive material is wholly or partially translucent, as recited in claim  16 .  
         [0029]     Additionally, the present invention is characterized by that the longitudinal hole is covered with a pad electrode with a larger diameter than a diameter of the longitudinal hole, as recited in claim  17 .  
         [0030]     The present invention is characterized by that the longitudinal hole is formed inside a lateral surface of the substrate at a constant distance from the lateral surface, as recited in claim  18 .  
         [0031]     The present invention is further characterized by that a pad electrode is disposed apart from the longitudinal hole on the other surface of the insulative substrate, and the pad electrode and the conductive material are electrically connected, as recited in claim  19 .  
         [0032]     The present invention is additionally characterized by that a diameter of the longitudinal hole ranges from 30 μm to 100 μm, as recited in claim  20 .  
         [0033]     The present invention is characterized by that a cross sectional shape of the longitudinal hole is tapered toward a depth direction, as recited in claim  21 .  
         [0034]     The present invention is further characterized by that the insulative substrate is a sapphire substrate, and the semiconductor thin film layer is a gallium nitride compound semiconductor layer, as recited in claim  22 .  
         [0035]     The present invention is characterized by that light is extracted mainly from the insulative substrate side, as recited in claim  23 .  
         [0036]     Additionally, the present invention is characterized by that a plurality of the longitudinal holes are formed, and conductive materials disposed in the plurality of the longitudinal holes are interconnected on the other surface of the insulative substrate, as recited in claim  24 .  
         [0037]     The present invention is characterized by that the longitudinal hole is formed by irradiating a laser from the insulative substrate side, as recited in claim  25 .  
         [0038]     Also, the present invention is characterized by that an inside of the longitudinal hole is cleaned by dry etching using chloride or fluoride gas after the longitudinal hole is formed, as recited in claim  26 .  
         [0039]     The present invention is characterized by a manufacturing method of a compound semiconductor light emitting device comprising laminating a plurality of semiconductor thin films to form a semiconductor layer on one surface of an insulative substrate in order to form an active layer, and providing one electrode on top surface of the semiconductor layer, and the method further comprising forming a longitudinal hole by laser-processing so as to have a depth reaching from the other surface of the insulative substrate to a first semiconductor thin film layer to be connected to the other electrode, and electrically connecting the electrode provided on the other surface of the insulative substrate and the first semiconductor thin film layer through a conductive material formed in the longitudinal hole, as recited in claim  27 .  
         [0040]     Also, the present invention is characterized by that a wafer including a plurality of the light emitting devices is divided into individual light emitting devices along grooves formed by laser-processing, as recited in claim  28 .  
         [0041]     The present invention is further characterized by that semiconductor layers damaged by laser-processing are removed by dry etching using chloride or fluoride gas after the grooves are formed, as recited in claim  29 .  
         [0042]     And the present invention is characterized by that laser-processing for forming the grooves are performed from the insulative substrate side, or from the laminated semiconductor layer side, or from both the insulative substrate side and the laminated semiconductor layer side, as recited in claim  30 . 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]      FIG. 1  is a bottom plan view from a rear side of a compound semiconductor light emitting device  1  according to a first embodiment of the present invention.  FIG. 2  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line II-II of  FIG. 1 .  FIG. 3  is a cross sectional view of an indicator including the compound semiconductor light emitting device according to the first embodiment of the present invention.  
         [0044]      FIG. 4  is a bottom plan view from a rear side of the compound semiconductor light emitting device  1  according to a second embodiment of the present invention.  FIG. 5  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line V-V of  FIG. 4 .  FIG. 6  is a bottom plan view of a device according to a modified example of the second embodiment of the present invention.  FIG. 7  is a bottom plan view of a device according to another modified example of the second embodiment of the present invention.  FIG. 8  is a cross sectional view of an indicator including the compound semiconductor light emitting device according to the second embodiment of the present invention.  
         [0045]      FIG. 9  is a bottom plan view from a rear side of the compound semiconductor light emitting device  1  according to a third embodiment of the present invention.  FIG. 10  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line X-X of  FIG. 9 .  
         [0046]      FIG. 11  is a bottom plan view from a rear side of the compound semiconductor light emitting device  1  according to a fourth embodiment of the present invention.  FIG. 12  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line X-X of  FIG. 11 .  
         [0047]      FIG. 13  is a bottom plan view from a rear side of the compound semiconductor light emitting device  1  according to a fifth embodiment of the present invention.  FIG. 14  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line X-X of  FIG. 13 .  FIG. 15  is a plan view of a device according to a modified example of the sixth embodiment of the present invention.  FIG. 16  is a plan view of a device according to another modified example of the sixth embodiment of the present invention.  
         [0048]      FIG. 17  is a bottom plan view from a rear side of the compound semiconductor light emitting device  1  according to a seventh embodiment of the present invention.  FIG. 18  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line X-X of  FIG. 17 .  
         [0049]      FIG. 19  is a bottom plan view from a rear side of the compound semiconductor light emitting device  1  according to an eighth embodiment of the present invention.  FIG. 20  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line X-X of  FIG. 19 .  FIG. 21  is a cross sectional view of an indicator including the compound semiconductor light emitting device according to the eighth embodiment of the present invention.  FIG. 22  is a bottom plan view of a device according to a modified example of the eighth embodiment of the present invention.  
         [0050]      FIG. 23  is a perspective view of a conventional device. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0051]     The present invention will be described in more details in conjunction with the accompanying drawings.  
         [0052]     A first embodiment will be described by referring to  FIGS. 1 and 2 .  FIG. 1  is a bottom plan view of a compound semiconductor light emitting device  1  according to the first embodiment of the present invention as seen from the rear side.  FIG. 2  is a cross sectional view of the compound semiconductor light emitting device  1  taken along the line II-II of  FIG. 1 .  
         [0053]     The device  1  is characterized by comprising a hole  2  which perpendicularly passes therethrough, as illustrated in  FIG. 2 . This through hole  2  is formed in a cylindrical or coned shape of 30 μm-100 μm in diameter by laser beams during laser-processing. The through hole  2  may also be formed in an hourglass shape with diameters of openings in the front and rear surfaces are wider than that in the middle.  
         [0054]     In this embodiment, the hole  2  of 50 μm in diameter is formed by laser-processing. It is preferable to irradiate the laser from the laminated semiconductor layer side. The hole  2  is used as a path conducting electricity in a perpendicular direction of the device (i.e. an electrical path). The electrical path is formed by filling inside the hole  2  with a conductive material  3 . One example to provide this conductive material  3  is to press conductive paste into the hole  2  to fill it up.  
         [0055]     The conductive material  3  may also be formed by plating. For example, after evaporating and depositing nickel (Ni) as seed on the front surface of the hole  2 , copper (Cu) is plated on the wall inside the hole  2  to serve as the conductive material  3 .  
         [0056]     Additionally, molten solder or metallic micro-balls may also be used instead of conductive paste to fill up the hole  2 .  
         [0057]     The device  1  comprises a semiconductor layer  4  formed by laminating two or more semiconductor thin films on a substrate  11 . The substrate  11  is an insulative substrate. For example, the substrate  11  is a sapphire substrate. In the device  1 , first conductivity type semiconductor layers and second conductivity type semiconductor layers are successively formed and laminated on a buffer layer  12  to form the semiconductor layer  4 . The buffer layer  12  is interposed between the substrate  11  and the semiconductor layer  4 .  
         [0058]     The buffer layer  12  and the semiconductor layer  4  are formed by MOCVD method for example. An example of the buffer layer  12  is an Al x Ga 1-x N (0≦X≦1) layer of 300 nm in thickness formed on the substrate  11 . An n-type contact layer  13  made of an n-type GaN layer of 3 μm in thickness doped with silicon (Si) for example is formed on this buffer layer  12 . An n-type cladding layer  14  made of n-type Al x Ga 1-x N (0≦X≦1) of approximately 300 nm in thickness doped with silicon (Si) for example is formed on the n-type contact layer  13 . A multi-quantum well structure active layer  15  having a composition of Al a In b Ga 1-a-b N (0≦a, 0≦b, a+b≦1) is formed on the n-type cladding layer  14 . A p-type cladding layer  16  made of p-type Al y Ga 1-y N (0≦Y≦1) of 300 nm in thickness doped with magnesium (Mg) for example is formed on the active layer  15 . A p-type contact layer  17  made of p-type GaN of 500 nm in thickness doped with magnesium (Mg) for example is formed on the p-type cladding layer  16 .  
         [0059]     The semiconductor layer  4  may also be formed directly on the substrate  11  without interposing the buffer layer  12 .  
         [0060]     A part of the n-type contact layer  13  (the first conductivity type semiconductor layer) is exposed by removing the semiconductor layers (including the second conductivity type semiconductor layers) laminated thereon and the exposed part of the contact layer  13  serves as an exposure region  10 . The removal of the semiconductor layer  4  is performed by a process including dry etching. The above-mentioned through hole  2  is provided in the exposure region  10 .  
         [0061]     To reduce damage to the semiconductor layer  4 , it is preferable to irradiate a laser from the same side where the semiconductor layer  4  is formed. Although the hole  2  is set to be a cylindrical shape with identical diameters from top to bottom, the completed hole  2  is slightly tapered. Alternately the through hole  2  may be formed by irradiating a laser from the substrate  11  side after irradiating the laser from the semiconductor layer  4  side. A laser which emits light at a wavelength to be absorbed in the substrate  1   1  is selected.  
         [0062]     Since the substrate  11  is a sapphire substrate, a short-wavelength laser of 500 nm or shorter is used here. In this embodiment, an ultra violet laser of wavelength 355 nm which is the third harmonic of a YAG laser categorized as a solid-state laser is employed. The laser beam is irradiated from the semiconductor layer  4  side to a possible center of the hole  2 , which will be the a center of an n-type electrode, for about one (1) second to form the hole  2  of 50 μm in diameter under the condition; repetition frequency (f) 3 kHz, scanning rate 0.5 mm/second, defocus(DF)-80 μm and power 1.85 W. The diameter of the hole  2  may range from 30 μm to 100 μm by controlling defocus(DF) and irradiating time.  
         [0063]     A YAG laser&#39;s fundamental frequency of 1,060 nm, second harmonic of 533 nm or fourth harmonic of 266 nm may also be employed.  
         [0064]     The hole  2  formed in this way is filled up with the conductive material  3 . Prior to filling the hole  2  with the conductive material  3 , parts of the semiconductor layer  4 , which were damaged through the laser process, are removed by dry etching. Chloride or fluoride gas may be used as etching gas when removing the damaged parts of the semiconductor layer by dry etching.  
         [0065]     The conductive material  3  may be filled as follows for example. First, the device is set upside down so that the semiconductor layer  4  is directed downward, and a mask made of an adhesive sheet is applied to the substrate  11 . A portion is cut out from the mask in desired size so that the conductive material is filled through the cutout portion. A conductive material such as conductive paste is filled in centering around the cutout portion of the mask. Being compressed by a spatula and so on, the conductive material is press-fitted into the hole  2 . The adhesive sheet which is the mask is peeled off after the conductive material  3  is press-fitted into the hole  2  and the hole  2  is filled up with the conductive material  3 . The conductive material  3  is then hardened by thermal treatment in a curing oven at a temperature of 200° C. for thirty minutes. After that, excess conductive material is removed by stripping solution, thereby completing the filling process of the conductive material  3  into the hole  2 .  
         [0066]     If necessary, the rear surface of the substrate  11  undergoes a backlapping process so that the thickness of the substrate  11  is reduced from 350 μm-430 μm to about 95 μm.  
         [0067]     An electrode  31  to make ohmic contact is formed on the exposure region  10  of the n-type contact layer  13 . The n-type ohmic electrode  31  is disposed on the exposure region  10  so as to make contact with the upper end of the through hole  2 . The n-type ohmic electrode  31  formed on the n-type contact layer  13  is electrically connected with the conductive material  3 . If the conductive material  3  formed in the through hole  2  can make ohmic contact with the n-type contact layer  13 , the conductive material  3  disposed in the through hole  2  may also serve as the electrode  31 . In other words, the formation of the electrode  31  may be omitted by forming the conductive material  3  capable of making ohmic contact with the n-type contact layer  13 . The conductive material  3  in the through hole  2  may serve as the electrode  31 . A metallic material used to form the electrode  31  may also be used for the conductive material  3  in the through hole  2 .  
         [0068]     An electrode  32  is formed on the p-type contact layer  17  to make ohmic contact therewith. The electrode  32  is formed to cover the entire surface of the p-type contact layer  17 . The electrode  32  is a reflective electrode to reflect light generated in the device  1 .  
         [0069]     The electrode  32  may be formed to cover only a part of the p-type contact layer  17  to reflect some of the light generated in the device  1 . The rest of the light, which was not reflected from this part, may be reflected from a member which is formed on the opposite side of the p-type contact layer  17  to the electrode  32 , and which reflects the wavelength of the light generated in the device  1 . When light is taken out from the electrode  32  side, the electrode  32  may be replaced with a light transmitting electrode through which light generated in the device  1  can pass.  
         [0070]     As illustrated in  FIGS. 1 and 2 , an electrode  33  is formed on the opposite surface (rear surface) of the substrate  11  to the surface where the semiconductor layer  4  is formed. The electrode  33  is electrically connected to the conductive material  3  disposed inside the through hole  2 . The conductive material inside the through hole  2  may also serve as the electrode  33 . The electrode  33  also serves as a pad electrode  34  with a predetermined thickness. Although in this embodiment, the pad electrode  34  is disposed to cover the through hole  2  as shown in  FIG. 1 , the pad electrode  34  may also be disposed apart from the through hole  2 . The pad electrode  34  is used for wire bonding. When the pad electrode  34  and the exposure region  10  are viewed as if they are on a plane, the electrode  34  and the exposure region  10  look overlapping one another. However, the pad electrode can be disposed so as not to overlap with the exposure region  10 , for example, to a position as will be seen in  FIG. 19 .  
         [0071]     A plurality of devices  1  are formed on a substrate of about two inches in diameter as a wafer (not shown). After that, the wafer is divided into dices to form individual devices. For dividing the wafer, the laser beam used for the formation of the through hole  2  may also be employed to form grooves for division. Grooves for division may be formed on the opposite surface of the substrate  11  to the surface where the semiconductor layer  4  is formed, or on the surface of the substrate  11  where the semiconductor layer  4  is formed, or both the opposite surface of the substrate  11  to the surface where the semiconductor layer  4  is formed and the surface of the substrate  11  where the semiconductor layer  4  is formed.  
         [0072]     When grooves for division are formed on the opposite surface of the substrate  11  to the surface where the semiconductor layer  4  is formed, the groove depth is set to extend from the rear surface of the substrate  11  to just before the active layer  15 . In this embodiment, the groove depth is set to be somewhat shorter than the thickness of the substrate  11  so that a part of the substrate  11  remains. Even when grooves are formed on the surface of the substrate  11  where the semiconductor layer  4  is formed, the groove depth for division is preferably set to be 20-70% of the thickness of the substrate  11 . Additionally, parts of the semiconductor layer  4 , which were damaged through laser-processing, should preferably be removed by dry etching. Chloride or fluoride gas may be used as etching gas when removing the damaged parts of the semiconductor layer by dry etching.  
         [0073]      FIG. 3  shows a light emitting apparatus comprising the light emitting device  1 . The light emitting device  1  is inverted so that the substrate  11  lies on top and is disposed on a first lead electrode  100 . The electrode  32  of the device  1  is electrically connected to the first lead electrode  100  via a conductive material  101 . Attention is needed only to adhere the lead electrode  100  immediately onto the conductive material  101 , and microscopic positioning is not needed. The electrode  31  and the n-type contact layer  13  should preferably be coated with an insulative material  102  to prevent the conductive material  101  from contacting them. The insulative material  102  for this coating should preferably be disposed in the device  1  in advance to cover the exposure region  10 . The pad electrode  34  at the substrate  11  side and a second lead electrode  103  are electrically connected through a bonding wire such as a gold wire  104 .  
         [0074]     When certain voltage or an electric current is supplied to the first and second electrodes  100  and  103 , an electrical path is formed through the first lead electrode  100 , the conductive material  101 , the electrode  32 , the semiconductor layer  4 , the electrode  31 , the conductive material  3 , the electrode  33 ( 34 ), the bonding wire  104  and the second lead electrode  103 , so that light can be taken out from the active layer  15 . If the light emitting device  1  is utilized for an LED indicator, the device  1 , the electrode  100  and  103  should preferably be molded with resin to improve the light extraction efficiency.  
         [0075]     Since each of the pair of electrodes is disposed respectively on one side and the other side of the substrate  11 , the amount of light shaded by the electrodes can be reduced as compared with a conventional example where both electrodes are disposed on the same side of the substrate, resulting in improvement of the light extraction efficiency. Furthermore, working efficiency in assembling work may also be improved because wire bonding is needed only once. The device can be mounted easily to a proper position by only aligning the p-type electrodes  32  with the base.  
         [0076]     Next, a second embodiment will be described by referring to  FIGS. 4 and 5 .  FIG. 4  is a bottom plan view of the device  1 , which corresponds to  FIG. 1 .  FIG. 5  is a cross sectional view taken along the line V-V of  FIG. 4 , which corresponds to  FIG. 1 . Same reference notes are given to components common with the first embodiment shown in  FIGS. 1 and 2 , and description of them will be omitted to avoid duplication of explanation. Differences will be described mainly.  
         [0077]     The device  1  is characterized by comprising a longitudinal hole  20  which perpendicularly extends to but does not pass through the n-type contact layer  13 . This longitudinal hole  20  is formed in a cylindrical or coned shape of 30 μm-100 μm in diameter by laser beams during laser-processing. The longitudinal hole  20  may also be formed in an hourglass shape with diameters of its openings and its bottom wider than that in the middle.  
         [0078]     In this embodiment, the longitudinal hole  20  of 50 μm in diameter is formed by laser-processing. The longitudinal hole  20  is used as a path conducting electricity in a perpendicular direction of the device (i.e. an electrical path). To form the electrical path, a conductive material  30  such as a metallic thin film is formed to cover the inner surface of the longitudinal hole  20 . Although the conductive material  30  is preferably formed by plating, which makes formation of the material throughout a microscopic area easier, it may also be formed by deposition of metal in such cases where the diameter of the hole is large or a tapered surface is formed. The longitudinal hole  20  may be filled up inside with a conductive material such as metallic materials.  
         [0079]     An example of forming the conductive material  30  by plating includes forming a deposited film of 20 nm in thickness on a wall inside the longitudinal hole  20  prior to plating copper (Cu) by deposition. The deposited film is made of titanium (Ti), platinum (Pt), gold (Au) or the like, each of which can make ohmic contact with the n-type contact layer  13 . Thus the conductive material  30 , or the plated layer is formed on the wall inside the longitudinal hole  20 . The conductive material  30   a  may be formed either by exclusively using materials capable of making ohmic contact with the n-type contact layer  11 , or by plating or providing the conductive paste or the like inside the longitudinal hole  20  in which a film, which is made of materials capable of making ohmic contact and which contacts with the n-type contact layer  11 , was formed.  
         [0080]     The metallic materials to be filled into the longitudinal hole  20  may include conductive paste, molten solder or metallic micro-balls.  
         [0081]     In the first embodiment, a part of the n-type contact layer  13  is exposed to form an exposure region by removing a part of the semiconductor layer  4  laminated thereon. In this embodiment, however, the surface, which makes contact with the semiconductor layer, of the contact layer  13  is formed in a same planar shape as that of the semiconductor layer including the p-type contact layer  17  thereon, thus there is no such exposure region on the contact layer  13 .  
         [0082]     The longitudinal hole  20  is formed by laser irradiation in the drilling process. To reduce the damage to the semiconductor layer  4 , it is preferable to irradiate the laser from the opposite surface (rear surface) of the substrate  11  to the surface (front surface) where the semiconductor layer  4  is formed. Although the longitudinal hole  20  is set to be a cylindrical shape with identical diameters from top to bottom, the completed hole  20  is slightly tapered. In this embodiment, for example, the rear surface of the substrate  11  may undergo a backlapping process so that the thickness of the substrate  11  is reduced from 350 μm-430 μm to about 45 μm before the laser irradiation. The longitudinal hole  20  is formed in a mortar-shape with diameters at the opening and the bottom part respectively 50 μm and 40 μm.  
         [0083]     A laser which emits light at a wavelength to be absorbed in the substrate  11  is selected, as in the first embodiment. Since the substrate  11  is a sapphire substrate, a short-wavelength laser of 500 nm or shorter is used here. In the second embodiment, as in the first embodiment, an ultra violet laser of wavelength 355 nm which is the third harmonic of a YAG laser categorized as a solid-state laser is employed. Other lasers such as YAG laser&#39;s fundamental frequency of 1,060 nm, second harmonic of 533 nm or fourth harmonic of 266 nm may also be employed.  
         [0084]     The intensity of the laser beam profile used herein shows a Gaussian distribution. The longitudinal hole  20  is formed to the extent that its end reaches the n-type contact layer  13  but not reaches the cladding layer  14 .  
         [0085]     As described above, the conductive material  30  connected to the n-type contact layer  13  comprises a metallic thin film suitable for making ohmic contact with the n-type contact layer  13 . An electrode  32  is formed on the p-type contact layer  17  to make ohmic contact therewith. The electrode  32  is formed to cover the entire surface of the p-type contact layer  17 . Alternately, the electrode  32  may be formed to cover only a part of the p-type contact layer  17 . The electrode  32  is a reflective electrode to reflect light generated in the device  1 .  
         [0086]     In such devices where light is taken out from the electrode  32  side, the electrode  32  may be replaced with a light transmitting electrode though which light generated in the device  1  can pass. Apart from being translucent, the electrode  32  may be a comb electrode or a mesh electrode made of light-shielding materials, both structured to transmit light. In the second embodiment, a part of the semiconductor layer  4  above the n-type electrode is not removed, which may maintain the broad light emitting area when light is taken out from the electrode  12  side.  
         [0087]     When light is not taken out from the electrode  32  side, light transmitted through the electrode  32  may be reflected by a member disposed on the opposite side of the electrode  32  to the p-type contact layer  17 . The member reflects the wavelength of light emitted from the device.  
         [0088]     As shown in  FIGS. 4 and 5 , an electrode  33 a is formed on the opposite surface of the substrate  11  to the surface where the semiconductor layer  4  is formed. The electrode  33   a  is electrically connected to the conductive material  30   a  disposed inside the longitudinal hole  20 . The conductive material  30  disposed inside the longitudinal hole  20  may also serve as the electrode  33   a . The electrode  33   a  also serves as a pad electrode  34   a  with a predetermined thickness. In the second embodiment, the pad electrode  34   a  is disposed to block the opening of the longitudinal hole  20  to minimize shading areas as shown in  FIG. 4 . The pad electrode  34   a  may also be disposed apart from the longitudinal hole  20  in the same way as shown in  FIG. 19 , which will be described later. The planar dimension of the pad electrode  34   a  is larger than that of the opening of the longitudinal hole  20 . The pad electrode  34   a  is used for wire bonding.  
         [0089]     As shown in  FIG. 4 , the pad electrode  34   a  and the longitudinal hole  20  are disposed at one corner of the substrate  11  in the second embodiment. As shown in  FIGS. 6 and 7 , however, they may also be disposed near the center of one side or at the center of the substrate  11  when viewed as a plane. The longitudinal hole  20  is disposed inside a lateral surface  11   a  of the substrate  11  at a constant distance from the lateral surface  11   a.    
         [0090]     As described above, a plurality of devices  1  are formed on a substrate of about two inches in diameter as a wafer (not shown). After that, the wafer is divided into dices to make individual devices. For dividing the wafer, a laser beam used for the formation of the longitudinal hole  20  may also be employed to form grooves for division. Grooves for division may be formed on the opposite surface of the substrate  11  to the surface where the semiconductor layer  4  is formed, or on the surface of the substrate  11  where the semiconductor layer  4  is formed, or both the opposite surface of the substrate  11  to the surface where the semiconductor layer  4  is formed and the surface of the substrate  11  where the semiconductor layer  4  is formed. When grooves for division are formed on the opposite surface of the substrate  11  to the surface where the semiconductor layer  4  is formed, the groove depth is set to extend from the rear surface of the substrate  11  to just before the active layer  15 . In this embodiment, the groove depth is set to be somewhat shorter than the thickness of the substrate  11  so that a part of the substrate  11  remains. Even when grooves are formed on the surface of the substrate  11  where the semiconductor layer  4  is formed, the groove depth for division is preferably set to be 20-70% of the thickness of the substrate  11 . Parts of the semiconductor layer  4 , which were damaged through laser-processing, are removed by dry etching.  
         [0091]     In the same manner of forming the grooves for division, deep grooves for making contact with the n-type contact layer  13  could be formed on the rear surface of the substrate  11  in the form of a wafer in the longitudinal and lateral directions so as to form a grid pattern. When the wafer having such a structure is divided, the division of the devices may start from the deep grooves, leading a high possibility of deformation of the devices.  
         [0092]     On the contrary, the longitudinal hole  20  formed in the above-mentioned embodiment is different in shape from the grooves for division. The division of the devices cannot start from the longitudinal hole  20 , thus preventing the deformation upon dividing the devices.  
         [0093]      FIG. 8  shows a light emitting apparatus comprising the light emitting device  1 . The light emitting device  1  is inverted and disposed on a first lead electrode  100  so that the substrate  11  lies on top for making the substrate  11  a light extraction surface. The electrode  32  of the device  1  is electrically connected to the first lead electrode  100  via a conductive material  101 . The pad electrode  34   a  at the substrate  11  side and a second lead electrode  103  are electrically connected through a bonding wire such as a gold wire  104 .  
         [0094]     When certain voltage or current is supplied to the second lead electrodes  100  and  103 , an electrical path is formed through the first lead electrode  100 , the conductive material  101 , the electrode  32 , the semiconductor layer  4 , the conductive material  30   a , the electrode  33   a  ( 34   a ), the bonding wire  104  and the second lead electrode  103  so that light can be taken out from the active layer  15 . Therefore, there are few places in the electrical path wherein electric fields are concentrated, resulting in a high ESD robustness.  
         [0095]     Light which is output from the active layer  15  is taken out of the device  1  through the substrate  11 . If the light emitting device  1  is utilized for an LED indicator, the device  1 , the electrodes  100  and  103  should preferably be molded with resin to improve the light extraction efficiency.  
         [0096]     Since each one of the pair of electrodes is disposed respectively on one side and the other side of the substrate  11 , light shaded by the electrodes can be reduced as compared with a conventional example where both electrodes are disposed on the same side of the substrate, which improves the light extraction efficiency. Furthermore, working efficiency in assembling work may also be improved because wire bonding is needed only once.  
         [0097]     Next, a third embodiment will be described by referring to  FIGS. 9 and 10 .  FIG. 9  is a bottom plan view of the device  1 , which corresponds to  FIG. 4 .  FIG. 10  is a cross sectional view taken along the line X-X of  FIG. 9 , which corresponds to  FIG. 5 . Same reference notes are given to components which are common with the first embodiment shown in  FIGS. 1 and 2 , and description of them will be omitted to avoid duplication of explanation. Differences will be described mainly.  
         [0098]     The third embodiment is characterized by adding a groove  35  and a conductive material  36  disposed therein to the second embodiment. In other words, the groove  35  which does not pass through the semiconductor device  1  is formed on the rear surface of the substrate  11 . The end of the groove  35  contacts the n-type contact layer  13 .  
         [0099]     As the above-mentioned longitudinal hole  20 , the groove  35  is formed by irradiating a laser. The groove  35  is joined to the longitudinal hole  20  and they are interconnected. The groove  35  is formed inside a lateral surface  11   a  of the substrate  11 , at a constant distance from the lateral surface  11   a  so that the groove  35  does not protrude beyond the lateral surface  11   a.  The groove  35  takes the form of a hollow square when viewed as a plane. The sides of the groove  35  extend along the outer edges of the substrate without intersecting each other so that the substrate outside the groove  35  is continuously remained like a frame. Thus an adverse effect caused by the groove  35  in dividing the devices can be reduced.  
         [0100]     A conductive material  36  is formed on surfaces of the groove  35 . Although the conductive material  36  is formed from the same material as, and simultaneously with the conductive material  30  used to form the electrical path in the longitudinal hole  20 , it may also be separately formed from a material of the same kind. The conductive material  36  makes ohmic contact with the n-type contact layer  13  to be electrically connected thereto. Therefore, the area in which the n-type contact layer  13  and the electrode  33   a  are electrically connected is larger than that of the second embodiment. If the conductive material  36  is formed by making a metal capable of making ohmic contact with the n-type contact layer  13  ultra-thin, the conductive material  36  may be a translucent material which light from the active layer  15  passes through. If the conductive material  30  is formed by making a metal capable of making ohmic contact with the n-type contact layer  13  ultra-thin, the conductive material  30  may be a translucent material which light from the active layer  15  passes through. The light extraction efficiency can be greatly improved, as compared to light shielding types of conductive materials, if the whole or a part of the conductive material  36  or the conductive material  30  is translucent. This light emitting device is also utilized in a light emitting apparatus like aforementioned embodiments.  
         [0101]     Next, a fourth embodiment will be described by referring to  FIGS. 11 and 12 .  FIG. 11  is a bottom plan view of the device  1 , which corresponds to  FIG. 1 .  FIG. 12  is a cross sectional view taken along the line X-X of  FIG. 11 , which corresponds to  FIG. 2 . Same reference notes are given to components which are common with the embodiment shown in  FIGS. 1 and 2 , and description of them will be omitted to avoid duplication of explanation. Differences will be described mainly.  
         [0102]     The fourth embodiment is characterized by adding a groove  35  and a conductive material  36  disposed therein to the first embodiment. In other words, the groove  35  which does not pass through the semiconductor device  1  is formed on the rear surface of the substrate  11 . The end of the groove  35  contacts the n-type contact layer  13 .  
         [0103]     As the above-mentioned through hole  2 , the groove  35  is formed by irradiating a laser. The groove  35  is joined to the through hole  2  and they are interconnected. The groove  35  is formed inside a lateral surface  11   a  of the substrate  11  so that the groove  35  does not protrude beyond the lateral surface  11   a  of the substrate  11 . A conductive material  3   a  is formed on the wall inside the through hole  2 .  
         [0104]     Similar to the third embodiment, the groove  35  takes the form of a hollow square when viewed as a plane. The electrode material  36  made of the same or the same kind of a material as the conductive material  3   a  for the electrical path formed on the wall inside the through hole  2  is formed inside the groove  35 . The electrode material  36  makes ohmic contact with the n-type contact layer  13  to be electrically connected thereto. Therefore, the area in which the n-type contact layer  13  and the electrode  33  are electrically connected is larger than that of the first embodiment.  
         [0105]     Next, a fifth embodiment will be described by referring to  FIGS. 13 and 14 .  FIG. 13  is a bottom plan view of the device  1 , which corresponds to  FIG. 1 .  FIG. 14  is a cross sectional view taken along the line X-X of  FIG. 13 , which corresponds to  FIG. 2 . Same reference notes are given to components which are common with the first embodiment shown in  FIGS. 1 and 2 , and description of them will be omitted to avoid duplication of explanation. Differences will be described mainly.  
         [0106]     The fifth embodiment is characterized by adding longitudinal holes  37 , electrode materials  38  disposed therein and an electrode  39  for connecting the electrode materials  38  at the rear surface of the substrate  11  to the first embodiment. In other words, a plurality of longitudinal holes  37  which do not pass through the semiconductor device  1  are formed on the rear surface of the substrate  11 . The ends of the longitudinal holes  37  contact the n-type contact layer  13 . As the above-mentioned through hole  2 , the longitudinal holes  37  are formed by irradiating a laser. The longitudinal holes  37  are formed independently without being joined to the through hole  2 . The longitudinal holes  37  are formed inside a lateral surface  11   a  of the substrate  11  so as not to protrude beyond the lateral surface  11   a  of the substrate  11 . The longitudinal holes  37  are formed in the vicinity of three corners of the substrate  11 , except a corner where the through hole  2  is disposed. A conductive material  3   b  is formed on the wall inside the through hole  2 . The electrode materials  38  made of the same or the same kind of a material as the conductive material  3   b  formed inside the through hole  2  is formed on the wall inside the longitudinal holes  37 . The conductive material  38  makes ohmic contact with the n-type contact layer  13  to be electrically connected thereto.  
         [0107]     The electrode  39  which connects the conductive material  3   b  in the though hole  2  and the electrode materials  38  in the longitudinal holes  37  is formed simultaneously with forming the electrode  33 . The conductive material  3   b  and the electrode materials  38  are interconnected on the rear side of the substrate  11  via the electrode  39 . The electrode materials  38  in the longitudinal holes  37  are also interconnected by the material of the electrode  33  which forms the pad electrode  34 . Therefore, the area in which the n-type contact layer  13  and the electrode  33  are electrically connected is larger than that of the first embodiment. Also, the area where the electrode inside the longitudinal holes  37  shades light can be smaller, as compared to the fourth embodiment.  
         [0108]     In each of the above-described embodiments, a pad electrode  40  of a certain thickness may be additionally formed on the electrode  32  as shown in  FIG. 14 , if the electrode  32  is a thin, light-transmitting type electrode, or an electrode is needed for the purpose of wire bonding.  
         [0109]     A sixth embodiment illustrated in  FIGS. 15 and 16  shows a formation of a mesa by means of etching circumferences of the p-type contact layer  17 , p-type cladding layer  16 , active layer  15  and n-type cladding layer  14  to expose the n-type contact layer  13  and a fabrication of an electrode on the exposed n-type contact layer to electrically connect the n-type contact layer  13  and the through hole  2 . These enable the electric current to be widely distributed through the semiconductor while preventing a current concentration on some p-n junction interfaces, thus enhancing ESD robustness.  
         [0110]     Next, a seventh embodiment will be described by referring to  FIGS. 17 and 18 .  FIG. 17  is a bottom plan view of the device  1 , which corresponds to  FIG. 4 . FIG.  18  is a cross sectional view taken along the line X-X of  FIG. 17 , which corresponds to  FIG. 5 . Same reference notes are given to components which are common with the above-described embodiments, and description of them will be omitted to avoid duplication of explanation. Differences will be described mainly.  
         [0111]     The seventh embodiment is characterized by adding longitudinal holes  37   a , conductive materials  38   a  disposed therein and an electrode  39   a  for connecting the conductive materials  38   a  at the rear surface of the substrate  11  to the second embodiment. A plurality of longitudinal holes  37   a  which do not pass through the semiconductor device  1  are formed on the rear surface of the substrate  11 . The ends of the longitudinal holes  37   a  contact the n-type contact layer  13 . As the above-mentioned longitudinal hole  20 , the longitudinal holes  37   a  are formed by irradiating a laser. The longitudinal holes  37   a  are formed independently without being joined to the longitudinal hole  20 . The longitudinal holes  37   a  are formed inside a lateral surface  11   a  of the substrate  11  so as not to protrude beyond the lateral surface  11   a  of the substrate  11 . The longitudinal holes  37  are formed in the vicinity of three corners of the substrate  11 , except a corner where the longitudinal hole  20  is disposed. The conductive materials  38   b  made of the same or the same kind of a material as the conductive material  31   a  formed inside the longitudinal hole  20  is formed on the wall inside the longitudinal holes  37   a . The conductive materials  38   b  make ohmic contact with the n-type contact layer  13  to be electrically connected thereto.  
         [0112]     The electrodes  33   a  and  39   a  which connect the conductive material  31   a  in the longitudinal hole  20  and the conductive materials  38   a  in the longitudinal holes  37   a  are formed by simultaneously forming both materials  33   a  and  39   a . The conductive material  31   a  and the conductive materials  38   b  are interconnected at the rear side of the substrate  11  via the electrode  39   a . The electrode material  31   a  in the longitudinal hole  20  and the conductive materials  38   b  in the longitudinal holes  37   a  are interconnected also by a material of the electrode  33   a  which forms the pad electrode  34 . If the electrode  39   a  is translucent, the electrode  33   a  on the electrode  39   a  should preferably be removed except for the pad electrode  34  to prevent the electrode  33   a  from shading light. Therefore, the area in which the n-type contact layer  13  and the electrode  33   a  are electrically connected is larger than that of the second embodiment. Also, the area where the material inside the longitudinal hole  20  shades light can be smaller, as compared to the third embodiment. Like aforementioned embodiments, this light emitting device is utilized in a light emitting apparatus with an arrangement where the substrate  11  lies on top as shown in  FIG. 8 .  
         [0113]     In each of the above-described embodiments, a pad electrode  40  of a certain thickness may be formed additionally on the electrode  32  as shown in  FIG. 18 , if the electrode  32  is a light-transmitting electrode or an electrode is needed for the purpose of wire bonding. By doing so, the device of  FIG. 18  can be incorporated as it is into the light-emitting apparatus of  FIG. 8 , in other words, the surface of the substrate  11  on which the semiconductor layer  4  is formed can be used as a light extracting surface. In this case, the electrode  33  on the substrate  11  side is connected with the first lead electrode  100 , while the electrode  40  on the opposite side is connected with the second lead electrode  103  with wire bonding.  
         [0114]     Next, an eighth embodiment will be described by referring to FIGS.  19  and.  20 .  FIG. 19  is a bottom plan view of the device  1 , which corresponds to  FIG. 4 .  FIG. 20  is a cross sectional view taken along the line X-X of  FIG. 19 , which corresponds to  FIG. 1 . Same reference notes are given to components which are common with the above-described embodiments and description of them will be omitted to avoid duplication of explanation. Differences will be described mainly.  
         [0115]     The eighth embodiment is characterized by that the cross sectional shape of the longitudinal hole  20  of the second embodiment is tapered toward the depth direction and that the pad electrode  34   b  connected to the conductive material  31   a  is disposed separately from the longitudinal hole  20   a . In other words, the shape of the longitudinal hole  20   a  is changed from a cylindrical shape to a truncated cone shape. Such a longitudinal hole  20   a  may be formed by laser-processing, for example, using a laser having intensity distribution in which intensity peaks of the laser with a Gaussian beam profile are truncated (beam profile of a shaped beam).  
         [0116]     Since the longitudinal hole  20   a  is shaped as described above, the conductive material  30   a  can be easily formed to a predetermined thickness on a wall inside the hole  20   a  from the rear side of the substrate  11  by deposition, sputtering and so on. Also, the slanted surface of the longitudinal hole  20   a  can be utilized as a light reflecting surface. Like aforementioned embodiments, this light emitting device is also utilized in a light emitting apparatus with an arrangement where the substrate  11  lies on top as shown in  FIG. 21 .  
         [0117]     Although the longitudinal hole  20   a  is disposed at the center of the substrate and the pad electrode  34   b  is disposed adjacently to the center of a side next to electrode  34   b , the disposition may be changed as shown in  FIG. 22 .  FIG. 22 ( a ) shows an example where the longitudinal hole  20   a  is disposed at the center of the substrate while the pad electrode  34   a  is disposed at a corner of the substrate  11 .  FIG. 22 ( b ) shows an example where the longitudinal hole  20   a  is disposed at one corner on one diagonal line of the substrate  11  while the pad electrode  34   b  is disposed at the other corner on the diagonal line of the substrate  11 .  FIG. 22 ( c ) shows an example where the longitudinal hole  20   a  is disposed adjacently to the center part of a side of the substrate  11  while the pad electrode  34   b  is disposed at a corner of the substrate  11 .  FIG. 22 ( d ) shows an example where the longitudinal holes  20   a  are disposed at both corners on one diagonal line of the substrate  11  while the pad electrode  34   b  is disposed at a corner on the other diagonal line of the substrate  34   a.    
         [0118]     Like aforementioned embodiments, this light emitting device is also utilized in a light emitting apparatus with an arrangement where the substrate  11  lies on top as shown in  FIG. 21 .  
         [0119]     The present invention is not limited to the embodiments described above, but can be modified in various ways without departing from subject matters of the invention. For example, the invention may be applicable to a device utilizing a semiconductor substrate other than an insulative substrate as the substrate  11 .  
         [0120]     As described above, the present invention realizes a high-efficiency light extraction. Also the present invention can enhance ESD robustness of a device.  
         [0121]     The device can be mounted easily to a proper position by only aligning the second conductivity type semiconductor layer with the base.  
         [heading-0122]     Industrial Applicability  
         [0123]     As described above, the compound semiconductor light emitting device of the present invention is suitable for a blue light emitting diode, a blue laser diode and the like.