Patent Publication Number: US-8541807-B2

Title: Semiconductor light emitting device and light emitting apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a 37 C.F.R. §1.53(b) continuation of U.S. patent application Ser. No. 12/188,755, filed Aug. 11, 2008 now U.S. Pat. No. 8,058,666 and claims priority under 35 U.S.C. 119 Korean Patent Application No. 10-2007-0079893(filed on Aug. 9, 2007), which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to a semiconductor light emitting device and light emitting apparatus having the same. 
     Group III-V nitride semiconductors have been variously applied to optical devices such as blue and green light emitting diodes (LEDs), high speed switching devices such as a MOSFET (Metal Semiconductor Field Effect Transistor) and an HEMT (Hetero junction Field Effect Transistor), and light sources of lighting devices or display devices. 
     The nitride semiconductor is mainly used for the LED or an LD (Laser Diode), and studies have been continuously conducted to improve the manufacturing process or a light efficiency of the nitride semiconductor. 
     SUMMARY 
     Embodiments provide a light emitting device that is designed to form a first electrode unit on a sidewall thereof and a light emitting apparatus having the light emitting device. 
     Embodiments provide a semiconductor light emitting device that is designed to form a first electrode unit on a sidewall of a substrate and a first conductive type semiconductor layer and a light emitting apparatus having the light emitting device. 
     Embodiments provide a semiconductor light emitting device that can form a first electrode unit on a lower-sidewall and a bottom surface thereof, and a light emitting apparatus having the light emitting device. 
     Embodiments provide a semiconductor light emitting device in which a first electrode unit near a bottom side thereof is mounted on a first electrode lead and a second electrode layer near the light emitting device side is mounted on a second lead electrode using a wire, and a light emitting apparatus having the light emitting device. 
     An embodiment provides a semiconductor light emitting device comprising: a substrate; a light emitting structure disposed on the substrate and comprising a first conductive type semiconductor layer, an active layer on the first conductive type semiconductor layer, and a second conductive type semiconductor layer on the active layer; a second electrode electrically connected to the second conductive type semiconductor layer; and a plurality of first electrodes disposed on a plurality of sidewalls of the first conductive type semiconductor layer, wherein the plurality of first electrodes are spaced apart from each other. 
     An embodiment provides a semiconductor light emitting device comprising: a substrate; a light emitting structure disposed on the substrate and comprising a first conductive type semiconductor layer, an active layer on the first conductive type semiconductor layer, and a second conductive type semiconductor layer on the active layer; and a plurality of first electrodes on a plurality of sidewalls of at least one of the substrate and the first conductive semiconductor layer, and being spaced apart from each other, wherein the plurality of first electrodes are physically separated from each other. 
     An embodiment provides a light emitting apparatus comprising: a semiconductor light emitting device comprising a first electrode and a second electrode; a first electrode lead disposed under the semiconductor light emitting device and electrically connected to the first electrode; and a second electrode lead electrically connected to the second electrode of the semiconductor light emitting device, wherein the semiconductor light emitting device comprises: a substrate; and a light emitting structure disposed on the substrate and comprising a first conductive type semiconductor layer, an active layer on the first conductive type semiconductor layer, and a second conductive type semiconductor layer on the active layer; wherein the first electrode comprises a plurality spaced apart from each other, the second electrode is in contact with a top surface of the second conductive type semiconductor layer, the second conductive type semiconductor layer is electrically connected to the active layer and the second electrode, and the active layer is electrically connected to the second conductive type semiconductor layer and the first conductive type semiconductor layer. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a semiconductor light emitting device according to a first embodiment. 
         FIG. 2  is a side sectional view taken along line A-A of  FIG. 1 . 
         FIG. 3  is a view of a light emitting apparatus having the semiconductor light emitting device of  FIG. 1 . 
         FIG. 4  is a side sectional view of a semiconductor light emitting device according to a second embodiment. 
         FIG. 5  is a side sectional view of a light emitting device according to a third embodiment. 
         FIG. 6  is a side sectional view of a semiconductor light emitting device according to a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to the embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  is a perspective view of a semiconductor light emitting device according to a first embodiment, and  FIG. 2  is a side sectional view taken along line A-A of  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , a light emitting device  100  comprises a substrate  110 , a buffer layer  120 , an undoped semiconductor layer  130 , a first conductive type semiconductor layer  140 , an active layer  150 , a second conductive type semiconductor layer  160 , a transparent electrode layer  170 , a first electrode layer  180 , and a second electrode layer  175 . 
     The substrate  110  may be formed of a material selected from the group consisting of sapphire (Al 2 O 3 ), GaN, SiC, ZnO, Si, GaP, GaAs, and a combination thereof. In the embodiment, the substrate  110  may be a conductive substrate such as a sapphire substrate. 
     A nitride semiconductor is grown on the substrate  110 . At this point, a physical vapor deposition apparatus, a chemical vapor deposition apparatus, a plasma laser deposition apparatus, a dual-type thermal evaporator sputtering apparatus, a metal organic chemical vapor deposition apparatus, and the like are used as a growing apparatus. 
     The buffer layer  120  is formed on the substrate  110  and the undoped semiconductor layer  130  is formed on the buffer layer  120 . Here, the buffer layer  120  is for reducing a lattice constant difference from the substrate  110 . The buffer layer  120  may be a GaN buffer layer, an AlN buffer layer, an AlGaN buffer layer, or an InGaN buffer layer. The undoped semiconductor layer  130  may be an undoped GaN layer to function as a substrate on which the nitride semiconductor is grown. 
     At least one of the buffer layer  120  and the undoped semiconductor layer  130  may be omitted. 
     The first conductive type semiconductor layer  140  is formed on the undoped semiconductor layer  130  and doped with first conductive dopants to function as an electrode contacting layer. The first conductive type semiconductor layer  140  may be realized as an N-type semiconductor layer. The N-type semiconductor layer may be formed of a III and V group compound such as InxAlyGal-x-yN (0≦x≦1, 0≦x≦1). That is, the N-type semiconductor layer may be formed of a material selected from the group consisting of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, and a combination thereof and provided in the formed of binary, ternary, or quaternary. The first conductive dopants are N-type dopants that comprise II-group elements such as Si, Ge, Sn, Te, and Se. 
     The first conductive type semiconductor layer  140  may have a thickness of 3˜30 um. The thickness T 1  may be formed with a thickness 3-6 times an N-type semiconductor of a typical LED structure. 
     Here, a semiconductor layer doped with dopants may be further formed between the undoped semiconductor layer  130  and the first conductive type semiconductor layer  140 . However, the present disclosure is not limited to this. 
     The active layer  150  is formed on the first conductive type semiconductor layer  140 . The active layer  150  has a single or multi-quantum well structure. The active layer  150  may be formed of, for example, a cycle of an InGaN well structure and a GaN barrier layer. However, the present disclosure is not limited to this. The light emitting material of the active layer  150  may be altered in accordance with a wavelength of light, such as blue, red, green wavelengths. 
     A conductive clad layer (not shown) may be formed on or under the active layer  150 . The conductive clad layer may be an AlGaN layer. 
     The second conductive type semiconductor layer  160  is formed on the active layer  150 . The second conductive type semiconductor layer  160  is doped with second conductive dopants to function as an electrode contacting layer. The second conductive type semiconductor layer  160  may be a P-type semiconductor layer that may be formed of a material selected from the group consisting of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, and a combination thereof. The second conductive dopants are P-type dopants that may be selected from the group consisting of Mg, Zn, Ca, Sr, Ba, and a combination thereof. 
     A third conductive type semiconductor layer (not shown) that is an N-type semiconductor layer may be formed on the second conductive type semiconductor layer  160 . In this embodiment, although it is described that the first conductive type semiconductor layer  140  is the N-type semiconductor layer and the second conductive type semiconductor layer  160  is the P-type semiconductor layer, it is also possible to form an inverse structure to this structure. In addition, the light emitting structure  165  may be one of a P-N junction structure, an N-P junction structure, a P-N-P junction structure, and an N-P-N junction structure. 
     The transparent electrode layer  170  is formed on the second conductive type semiconductor layer  160  and the second electrode layer  175  is formed on the transparent electrode layer  170 . Here, the transparent electrode layer  170  is a transmittable oxide layer formed of a material selected from the group consisting of ITO, ZnO, RuOx, TiOx, IrOx, and a combination thereof. When the light emitting structure is the N-P-N junction structure, the transparent electrode layer  170  may be formed on the third conductive type semiconductor layer that is the N-type semiconductor layer. 
     The second electrode layer  175  comprises a second electrode pad that may be formed in a single or multi-layer using Ti, Au, Pd, Ni, or an alloy thereof. The second electrode layer  175  may be formed in a stacked structure of a second reflective electrode (not shown) and a second electrode pad (not shown). The second reflective electrode may be formed in a single or multi-layer using Al, Ag, Pd, Rh, Pt, and an alloy thereof. The second electrode pad may be formed on the second reflective electrode. 
     A first electrode unit  180  is formed on a lower-outer surface of the light emitting device  100 . The first electrode unit  180  may be formed on opposite two sidewalls among the sidewalls of the light emitting device  100 . In addition, the first electrode unit  180  may be formed on one sidewall, left and right sidewalls  101 , or/and front and rear walls ( 103 ). 
     The first electrode unit  180  comprises a sidewall layer  180 A and a bottom layer  180 B. The sidewall layer  180 A is formed on sidewalls of the substrate  110 , buffer layer  120 , undoped semiconductor layer  130 , and first conductive type semiconductor layer  140 . The sidewall layer  180 A may be formed on the opposite two sidewalls  101  among the four sidewalls of the light emitting device  100 . However, the present disclosure is not limited to this configuration. 
     The sidewall layer  180 A of the first electrode unit  180  may extend from a lower end of the first conductive type semiconductor layer  140  to a predetermined height T 2 . Upper ends  182  and  186  of the sidewall layer  180 A of the first electrode unit  180  are higher than lower end of the first conductive type semiconductor layer  140  but lower than the active layer  150 . 
     The bottom layer  180 B is electrically connected to the sidewall layer  180 A and formed on a bottom surface  105  of the substrate  110 . 
     The first electrode unit  180  comprises a first reflective electrode  181  and a first electrode pad  185 . The first reflective electrode  181  is formed in a single or multi-layer of a reflective material such as Al, Ag, Pd, Rh, Pt, and an alloy thereof. The first electrode pad  185  is formed on an outer surface of the first reflective electrode  181  in a single or multi-layer formed of a material selected from the group consisting of Ti, Al, In, Ta, Pd, Co, Ni, Si, Ge, Ag, Au, and a combination thereof. 
     Here, the first electrode unit  180  may be formed with the first electrode pad  185  without the first reflective electrode  181 . In addition, the sidewall layer  180 A of the first electrode unit  180  may be a transmittable electrode and the bottom layer  180 B may be formed with the first electrode pad  185 . The transmittable electrode may be formed of a material selected from the group consisting of ITO, ZnO, RuOx, TiOx, IrOx, SnO2, and a combination thereof. In addition, the first reflective electrode  181  may be formed of a material having ohmic and reflectance properties. 
     The first electrode unit  180  reflects the light traveling toward the substrate to improve the light emitting efficiency of the light emitting device  100 . In addition, the transmittance and reflectance properties of the first electrode unit  180  improve the light emitting efficiency of the semiconductor light emitting device  100 . 
     In addition, since the semiconductor light emitting device  100  is manufactured without performing a mesa etching process, the reduction of the light emitting area of the active layer  150  can be prevented. 
     Since the first electrode unit  180  supplies the current to the sidewall of the first conductive type semiconductor layer  140 , the current can be uniformly diffused through an entire area of the first conductive type semiconductor layer  140 . Therefore, the internal quantum efficiency of the active layer  150  can be improved. 
       FIG. 3  is a view of a light emitting apparatus having the semiconductor light emitting device of  FIG. 1 . 
     Referring to  FIG. 3 , a light emitting apparatus  200  comprises a light emitting device  100 , a first electrode lead  106 , a second electrode lead  107 , and a wire  108 . 
     In the semiconductor light emitting device  100 , the first electrode unit  180  near the bottom side is mounted on the first electrode lead  106  by metal paste and the second electrode layer  175  is connected to the second electrode lead  107  by the wire  108 . Here, the metal paste may be selected from the group consisting of Cu, Ag, Au, Pd, Pt, Ni, Al, and an alloy thereof. However, the present disclosure is not limited to this. Here, the first and second electrode leads  106  and  107  may be provided in the form of lead frames or plating layer. 
     Since only one wire is used for the semiconductor light emitting device  100 , interference of light emitted from the light emitting device  100  can be reduced. 
       FIG. 4  is a side sectional view of a semiconductor light emitting device according to a second embodiment. In the second embodiment, a description of the same parts as the first embodiment will be omitted. 
     Referring to  FIG. 4 , a semiconductor light emitting device  100 A comprises a dielectric  190  on an upper-sidewall thereof. 
     The dielectric  190  extends from both ends  182  and  186  of the first electrode unit  180  to a sidewall of the transparent electrode layer  170 . The dielectric  190  may further extend up to an outer top surface of the transparent electrode layer  170 . That is, the dielectric  190  may extend from an outer-upper portion of the first conductive type semiconductor layer  180  to outer sides of the second conductive type semiconductor layer  160  and transparent electrode layer  170 . 
     A thickness T 4  of the dielectric  190  may be same as a thickness T 3  of the first electrode unit  180  but not limited to this. 
       FIG. 5  is a side sectional view of a semiconductor light emitting device according to a third embodiment. In the third embodiment, a description of the same parts as the first embodiment will be omitted. 
     Referring to  FIG. 5 , a semiconductor light emitting device  100 B comprises a substrate  110  provided with a protrusion/groove pattern  112 . That is, the protrusion/groove pattern  112  is formed on a top surface of the substrate  110  and the protrusion/groove pattern  112  may comprise at least one of a plurality of stripe-shaped protrusions, a plurality of lens-shaped protrusions, and a plurality of a cone-shape protrusions. 
       FIG. 6  is a side sectional view of a semiconductor light emitting device according to a fourth embodiment. In the fourth embodiment, a description of the same parts as the first embodiment will be omitted. 
     Referring to  FIG. 6 , a semiconductor light emitting device  100 C comprises a conductive substrate  110 A and a first electrode unit  180 A formed on a lower sidewall thereof. The conductive substrate  110 A is formed of, for example, GaN, GaAs, GaP, InP, and the like. 
     The first electrode unit  180 A is formed on a lower sidewall, extending from a sidewall of the conductive substrate  110 A to a lower sidewall of the first conductive type semiconductor layer  140 . The first electrode unit  180 A may be formed on one sidewall, opposite sidewalls, or all sidewalls. 
     The first conductive type semiconductor layer  140  may be applied with a current through the conductive substrate  110 A and the first electrode unit  180 A. 
     The light emitting devices of the first to fourth embodiments may employ constitutional elements of other embodiments and are not limited to their structures. In addition, since the light emitting device uses only one wire, problems such as a bonding problem and a light interference problem can be solved. In addition, an etching process is not performed for the active layer, the reduction of the light emitting of the active layer can be prevented. Further, by forming the first electrode unit on the lower portion and sidewalls of the substrate, an amount of light reflected can increase. 
     In the embodiments, since the current is supplied to the first conductive type semiconductor layer through the first electrode unit formed on the sidewall of the light emitting device, the first conductive type semiconductor layer is uniformly applied with the current and thus the light can be emitted from the active layer with a uniform distribution. 
     In the description, it is understood that when a layer (or film) is referred to as being ‘on’ another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being ‘under’ another layer, it can be directly under the other layer, and one or more intervening layers may also be present. In addition, “on” and “under” of each layer will be referred based on the drawings. Further, the thickness of each layer is exemplarily illustrated and thus the actual thickness of each layer is not limited to the drawings. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is comprised in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.