KR20060035464A - Light-emitting device having reflective layer formed under electrode - Google Patents

Abstract

The present invention discloses a light emitting device comprising a substrate, an n-type electrode, an active layer, a p-type semiconductor layer, a reflective layer, and a p-type electrode. The n-type electrode is located on the bottom side of the substrate and the active layer is located on the top side of the substrate. The p-type semiconductor layer covers the active layer. The reflective layer is positioned over the p-type semiconductor layer, and the p-type electrode covers the reflective layer. The reflective layer is a conductive layer with high reflectivity and is formed below the p-type electrode to avoid light of the light emitting device being absorbed by the metal electrode.

Description

Light-emitting device having a reflective layer formed under the electrode {LIGHT-EMITTING DEVICE HAVING REFLECTIVE LAYER FORMED UNDER ELECTRODE}

1 is a structural diagram of a light emitting diode according to the prior art.

2 is a structural diagram of another light emitting diode according to the prior art;

3 is a structural diagram of a light emitting diode according to the present invention;

4 is a structural diagram of another light emitting diode according to the present invention;

5 is a schematic structural diagram of an embodiment according to the present invention;

6A-6C are schematic structural diagrams showing contact on a rough surface according to the present invention.

7 is a schematic structural diagram showing contact of a reflective layer with a semiconductor layer of one embodiment according to the present invention;

<Explanation of symbols for the main parts of the drawings>

10,20,30,40: light emitting diodes 11,21,31,41: substrate

12,22,32,42: dispersed Bragg reflector 13,23,33,43: active layer

14,24,34,44: p-type semiconductor layer 15,25,35,45: p-type electrode

16, 26, 36, 46: n-type electrode 27, 47: n-type semiconductor layer

38,48: reflective layer

The present invention relates to a semiconductor light emitting device, and more particularly to a light emitting diode having a high lighting efficiency.

1 is a structural diagram of a light emitting diode according to the prior art. As shown in FIG. 1, the light emitting diode 10 includes a substrate 11, a distributed Bragg reflector (DBR) 12, an active layer 13, a p-type semiconductor layer 14, and a p-type electrode ( 15, and an n-type electrode 16 positioned below the substrate 11. The substrate 11 is an n-type GaAs substrate, and the DBR 12 has a multilayer reflective structure in order to reflect light. The active layer 13 is composed of an n-type AlGaInP lower cladding layer, an AlGaInP active layer, and a p-type AlGaInP upper cladding layer. The p-type semiconductor layer 14 is an ohmic contact layer, and the material of this layer is AlGaAs, AlGaInP, or GaAsP. The p-type electrode 15 and the n-type electrode 16 are metal electrodes for wiring bonding.

2 is a structural diagram of another light emitting diode according to the prior art. As shown in FIG. 2, the light emitting diode 20 includes a substrate 21, a distributed Bragg reflector (DBR) 22, an n-type semiconductor layer 27, an active layer 23, a p-type semiconductor layer 24, The p-type electrode 25 and the n-type electrode 26 are included. In the manufacturing process of the light emitting diode 20, first, the DBR 22, the n-type semiconductor layer 27, the active layer 23, and the p-type semiconductor layer 24 are formed on the substrate 21. Thereafter, an etching process is performed to expose a portion of the n-type semiconductor layer 27, and a p-type electrode 25 is formed over the p-type semiconductor layer 24. Finally, the n-type electrode 26 is formed on the exposed n-type semiconductor layer 27. Similarly, the substrate 21 is a GaAs substrate, and the DBR 22 has a multilayer reflective structure to reflect light. The active layer 23 is composed of an n-type AlGaInP lower cladding layer, an AlGaInP active layer, and a p-type AlGaInP upper cladding layer. The p-type semiconductor layer 24 and the n-type semiconductor layer 27 are resistive contact layers, and their materials may be AlGaAs, AlGaInP, or GaAsP. The p-type electrode 25 and the n-type electrode 26 are metal electrodes for wiring bonding.

However, when operating the above-described light emitting diodes, the p-type and n-type electrodes absorb light from the active layer, thereby decreasing the lighting efficiency.

Accordingly, the main object of the present invention as claimed is to provide a light emitting diode having a high illumination efficiency in order to solve the above problems. Such light emitting diodes have a reflective layer located underneath the metal electrodes to avoid absorption of light.

According to the claimed invention, a semiconductor light emitting device comprises a substrate, an n-type electrode, an active layer, a p-type semiconductor layer, a reflective layer, and a p-type electrode. The n-type electrode is located on the bottom side of the substrate and the active layer is located on the top side of the substrate. The p-type semiconductor layer covers the active layer. The reflective layer is positioned over the p-type semiconductor layer, and the p-type electrode covers the reflective layer. The reflective layer is a conductive layer with high reflectivity.

The claimed invention further discloses a semiconductor light emitting device comprising a substrate, an n-type semiconductor layer, an active layer, an n-type electrode, a p-type semiconductor layer, a first reflective layer, and a p-type electrode. The n-type semiconductor layer covers the substrate, and the active layer and the n-type electrode individually cover portions of the n-type semiconductor layer. The p-type semiconductor layer covers the active layer. The first reflective layer is positioned over the p-type semiconductor layer, and the p-type electrode covers the first reflective layer. The semiconductor light emitting device further includes a second reflective layer located between the n-type semiconductor layer and the n-type electrode. Both the first reflecting layer and the second reflecting layer are conductive layers having high reflectivity.

These and other objects of the present invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments of the invention, which is described in conjunction with the various figures.

Referring to FIG. 3, which is a structural diagram of the first embodiment of the present invention, the light emitting diode 30 includes a substrate 31, a distributed Bragg reflector (DBR) 32, an active layer 33, a p-type semiconductor layer 34, and p. A type electrode 35, an n-type electrode 36, and a reflective layer 38. In the manufacturing process of the light emitting diode 30, first, the DBR 32, the active layer 33, and the p-type semiconductor layer 34 are formed on the substrate 31. Thereafter, the reflective layer 38 is formed on a portion of the p-type semiconductor layer 34. Finally, the p-type electrode 35 is formed over the reflective layer 38, and the n-type electrode 36 is formed over the other surface of the substrate 31.

The substrate 31 is a conductive material such as n-type GaAs or GaN, and the DBR 32 is formed of a multilayer reflective structure such as AlAs and GaAs to reflect light. The active layer 33 has a uniform structure, a single heterojunction structure, a double heterostructure (DH) structure, or a multiple quantum well (MQW) structure. If the structure of the active layer 33 is a double heterojunction structure, it may be composed of an n-type AlGaInP lower cladding layer, an AlGaInP active layer, and a p-type AlGaInP upper cladding layer. Since various structures of the active layer are known in the art, they are not described herein any further. The p-type semiconductor layer 34 is a resistive contact layer composed of a plurality of p-type III-V compound layers such as GaN, AlGaAs, AlGaInP, or GaAsP doped with Mg or Zn. A p-type semiconductor layer comprising a plurality of p-type III-V compound layers is shown, for example, in FIG. 5. The p-type electrode 35 and the n-type electrode 36 are metal electrodes for wiring bonding.

Reflective layer 38 is a conductive layer having a high reflectivity such as silver (Ag), aluminum (Al), gold (Au), chromium (Cr), platinum (Pt) or rhodium (Rh). It can be a single layer or a multilayer structure. Reflective layers comprising a multilayer structure are schematically illustrated in FIG. 5, for example. Reflective layer 38 is used to reflect light from active layer 33 to the surroundings without being absorbed by p-type electrode 35. In addition, the reflective layer 38 and the p-type semiconductor layer 34 may be in contact with the rough surface. The rough surface results from the etching process and may be formed to have an inclined or curved structure with a specific reflection angle to strengthen the reflective layer 38, for example, as shown in FIGS. 6A-6C. Reflective layer 38 may also be a scattering layer, such as a transparent conductive material comprising a plurality of diffusers, to partially reflect light from active layer 33 to reduce absorption of light by p-type electrode 35. Can be. The scattering layer has a scattering ratio of 50% or more.

Reference is made to FIG. 4, which is a structural diagram of a second embodiment of the present invention. As shown in FIG. 4, the light emitting diode 40 includes a substrate 41, a distributed Bragg reflector (DBR) 42, an active layer 43, a p-type semiconductor layer 44, a p-type electrode 45, and n. The type electrode 46, the n-type semiconductor layer 47, the first reflective layer 48, and the second reflective layer 49 are included. In the manufacturing process of the light emitting diode 40, first, the DBR 42, the n-type semiconductor layer 47, the active layer 43, and the p-type semiconductor layer 44 are formed on the substrate 41. Thereafter, an etching process is performed on the p-type semiconductor layer 44 and a part of the active layer 43 to expose a portion of the n-type semiconductor layer 47. After that, the first reflective layer 48 and the p-type electrode 45 are formed on the unetched p-type semiconductor layer 44, and the second reflective layer 49 and n are exposed on the exposed n-type semiconductor layer 47. The type electrode 46 is formed. The etching process may be a wet etching process, a dry etching process or a process in which these two processes are alternated. Moreover, the first reflecting layer 48 and the second reflecting layer 49 may be designed selectively or simultaneously in the light emitting diode 40 as required.

In the second embodiment, the substrate 41 is a non-conductive material such as sapphire, and the DBR 42, the active layer 43 and the p-type semiconductor layer 44 are similar to those of the first embodiment. The n-type semiconductor layer 47 is an ohmic contact layer composed of a plurality of n-type III-V compound layers such as undoped GaN, Si doped GaN, AlGaAs, AlGaInP, or GaAsP. The p-type and n-type semiconductor layers comprising a plurality of Group III-V compound layers are schematically illustrated, for example, in FIG. The p-type electrode 45 and the n-type electrode 46 are metal electrodes for wiring bonding.

The first reflective layer 48 and the second reflective layer 49 also have a high reflectivity such as silver (Ag), aluminum (Al), gold (Au), chromium (Cr), platinum (Pt) or rhodium (Rh). Layer, and the first reflective layer 48 and the second reflective layer 49 may be a single layer or multiple layers. Reflective layers comprising a multilayer structure are schematically illustrated in FIG. 7, for example. The first reflective layer 48 and the second reflective layer 49 are used to reflect light from the active layer 43 to the surroundings without being absorbed by the p-type electrode 45 and the n-type electrode 46. In addition, the reflective layers 48 and 49 and the p-type and n-type semiconductor layers 44 and 47 may be in contact with the rough surface. The rough surface results from the etching process and may be formed to have an inclined or curved structure with a specific reflection angle to strengthen the reflective layers 48 and 49, for example, similar to those shown in FIGS. 6A-6C. Reflective layers 48 and 49 also include a plurality of diffusers to partially reflect light from active layer 43 to reduce absorption of light by p-type electrode 45 and n-type electrode 46. It may be a scattering layer such as a conductive material. The scattering layer has a scattering ratio of 50% or more.

In contrast to the prior art, the present invention having a reflective layer with high reflectivity can avoid the light from the active layer being absorbed by the metal electrode, so that the light from the active layer can be used completely.

Those skilled in the art will readily appreciate that various modifications and adaptations of the device may be made while maintaining the teachings of the present invention. Accordingly, the above disclosure should be construed as limited only by the limitations and limitations of the appended claims.

Claims (22)

As a semiconductor light emitting device, Substrate, An n-type electrode on the bottom surface of the substrate, An active layer located on an upper surface of the substrate; A p-type semiconductor layer covering the active layer, A reflective layer on the p-type semiconductor layer; And a p-type electrode covering said reflective layer. The semiconductor light emitting device of claim 1, wherein the substrate is a conductive material. The semiconductor light emitting device of claim 1, wherein the p-type semiconductor layer comprises a plurality of p-type Group III-V compound layers. The semiconductor light emitting device of claim 1, wherein the reflective layer is a conductive layer having a predetermined reflectivity, and the reflective layer reflects light from the active layer to avoid light being absorbed by the p-type electrode. The semiconductor light emitting device of claim 4, wherein the reflective layer has a single layer structure. The semiconductor light emitting device of claim 4, wherein the reflective layer has a multilayer structure. The semiconductor light emitting device of claim 4, wherein the reflective layer comprises silver (Ag), aluminum (Al), gold (Au), chromium (Cr), platinum (Pt), or rhodium (Rh). The semiconductor light emitting device of claim 1, wherein the reflective layer is a conductive layer having a predetermined scattering ratio, and the reflective layer partially reflects light from the active layer to reduce light being absorbed by the p-type electrode. The semiconductor light emitting device of claim 1, wherein the reflective layer and the p-type semiconductor layer are in contact with a rough surface, and the rough surface has an inclined or curved structure having a specific reflection angle to strengthen the reflective layer. The semiconductor light emitting device of claim 1, further comprising a distributed Bragg reflector (DBR) positioned between the substrate and the active layer. As a semiconductor light emitting device, Substrate, An n-type semiconductor layer covering the substrate; An active layer and an n-type electrode which individually cover portions of the n-type semiconductor layer, A p-type semiconductor layer covering the active layer, A first reflective layer on the p-type semiconductor layer, And a p-type electrode covering said first reflective layer. The semiconductor light emitting device of claim 11, wherein the substrate is a nonconductive material. 12. The semiconductor light emitting device of claim 11, wherein the n-type semiconductor layer comprises a plurality of n-type III-V compound layers, and the p-type semiconductor layer comprises a plurality of p-type III-V compound layers. . 12. The semiconductor light emitting device of claim 11, further comprising a second reflective layer positioned between the n-type semiconductor layer and the n-type electrode. 15. The method of claim 14, wherein the first reflecting layer and the second reflecting layer are both conductive layers having a predetermined reflectivity, the first reflecting layer and the second reflecting layer reflects light from the active layer, the light is the p-type electrode And a semiconductor light emitting device which avoids being absorbed by the n-type electrode. The semiconductor light emitting device of claim 15, wherein the second reflective layer and the n-type semiconductor layer are in contact with a rough surface, and the rough surface has an inclined or curved structure having a specific reflection angle to reinforce the second reflective layer. 16. The semiconductor light emitting device according to claim 15, wherein both of the first reflective layer and the second reflective layer have a single layer structure. The semiconductor light emitting device of claim 15, wherein both of the first reflective layer and the second reflective layer have a multilayer structure. The semiconductor light emitting device of claim 15, wherein the first reflective layer and the second reflective layer include silver (Ag), aluminum (Al), gold (Au), chromium (Cr), platinum (Pt), or rhodium (Rh). device. 15. The method of claim 14, wherein the first reflective layer and the second reflective layer are both conductive layers having a predetermined scattering ratio, and the first reflective layer and the second reflective layer partially reflect light from the active layer so that the light A semiconductor light emitting device which reduces absorption by p-type electrodes and n-type electrodes. 12. The semiconductor light emitting device of claim 11, wherein the first reflective layer and the p-type semiconductor layer are in contact with a rough surface, and the rough surface has an inclined or curved structure having a specific reflection angle to strengthen the first reflective layer. . 12. The semiconductor light emitting device of claim 11, further comprising a distributed Bragg reflector (DBR) positioned between the substrate and the n-type semiconductor layer.

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