JP2007103690A - Semiconductor light emitting device and its fabrication process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a reflective electrode of a metal having high reflectivity without decreasing the reflectivity. <P>SOLUTION: A semiconductor light emitting device includes an n-type semiconductor layer 11, a p-type semiconductor layer 13, and an active layer 12 having a multilayer quantum well structure sandwiched by the n-type semiconductor layer and the p-type semiconductor layer. A reflective electrode 14 is formed of a metal exhibiting high reflectivity to emission light from the active layer 12 on the p-type semiconductor layer 13, a nonmetallic protective layer 15 is formed on the reflective electrode 14, and a first cover electrode 16 electrically connected with the reflective electrode 14 through an opening groove 15a is formed on the protective layer 15. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device and a method for manufacturing the same, and more particularly to a semiconductor light emitting device having a reflective electrode having a high reflectance and a method for manufacturing the same.

  In recent years, light emitting devices using semiconductors have been widely used in applications such as display light sources, liquid crystal backlight light sources, and illumination white light sources, and high output of semiconductor light emitting devices is strongly desired. ing. In particular, light emitting devices made of nitride semiconductors, that is, light emitting diode (LED: light emitting diode) devices capable of obtaining light emitted from the blue region to the ultraviolet region, due to high output, are used in large markets such as lighting applications and automotive headlamp applications. Can be expected. In order to realize a semiconductor light emitting device capable of high output, not only the luminous efficiency of the light emitting layer itself is increased, but also a structure that efficiently extracts the emitted light generated in the light emitting layer to the outside, that is, the extraction efficiency. Is extremely important.

  As a method for improving the extraction efficiency of emitted light, the electrode material formed on the semiconductor layer has translucency, the electrode is patterned, the surface of the electrode or the semiconductor layer is processed into an uneven shape, Various techniques for coating the semiconductor layer with a resin having a low refractive index have been proposed.

  Among them, a great effect is expected, a structure in which light is extracted from the back side of the substrate by using a metal having high reflectivity such as silver (Ag) or aluminum (Al) as a reflective electrode, so-called flip. A light-emitting device having a chip-type structure. Ag and Al are materials having high reflectivity from the ultraviolet region to the visible region, but on the other hand, there are problems such as large migration and weakness to heat, making it difficult to put it into practical use as a reflective electrode.

  In particular, in an LED device using a nitride semiconductor, an annealing process at a high temperature of 400 ° C. or higher is required to form a good ohmic electrode. In this annealing process, mutual diffusion occurs between Ag or Al constituting the reflective electrode and gold (Au) constituting the cover electrode provided so as to cover the reflective electrode in consideration of durability. There is a problem in that the reflectance of the reflective electrode made of, for example, decreases.

  Also, when the LED device is mounted, since it is subjected to a heat treatment of about 300 ° C. in the mounting process to the submount and the wire bonding process, the reflectance is reduced due to the mutual diffusion of Ag and the like. .

  In order to prevent a decrease in reflectance of the reflective electrode due to mutual diffusion between the metals constituting the reflective electrode and the cover electrode, the reflective electrode and the cover as described in Patent Document 1 or Patent Document 2 below are used. A method has been proposed in which a metal film for preventing diffusion is provided between the electrodes and the metal constituting the reflective electrode and the cover electrode is prevented from interdiffusion, thereby preventing the reflectance of the reflective electrode from decreasing.

  FIG. 12 shows the structure of a conventional semiconductor light emitting device described in Patent Document 1. As shown in FIG. 12, the conventional semiconductor light emitting device has an n-type semiconductor layer 102, an active layer 104, and a p-type semiconductor layer 105 sequentially formed by epitaxial growth on a substrate 101 made of sapphire. On the p-type semiconductor layer 105, a reflective layer 106 made of silver (Ag) with a thickness of 100 nm, a diffusion prevention layer 107 made of nickel (Ni) with a thickness of 300 nm, and gold (Au) with a thickness of 50 nm. The wiring metal layers 108 are sequentially formed. An n-side electrode 103 is formed in a region where a part of the n-type semiconductor layer 102 is exposed.

  The semiconductor light emitting device thus formed is flip-chip mounted with the n-side electrode 103 and the wiring metal layer 108 facing a submount (not shown). As a result, the emitted light emitted from the active layer 104 is reflected by the reflective layer 106, passes through the substrate 101, and is extracted outside.

According to Patent Document 1, by providing a diffusion prevention layer 107 made of Ni between the reflective layer 106 and the wiring metal layer 108, heat treatment between Au constituting the wiring metal layer 108 and Ag constituting the reflective layer 106. It is described that mutual diffusion due to can be prevented.
Japanese Patent Laid-Open No. 11-186598 JP 2002-26392 A

  However, as a result of various studies, the present inventors have found that the diffusion preventing layer 107 provided in the conventional semiconductor light emitting device cannot sufficiently obtain the effect of preventing interdiffusion between Au and Ag. The conclusion is obtained. In particular, when heat treatment is performed after the reflective layer 106 is formed, interdiffusion between Au and Ag occurs, and there is a problem that the reflectance of the reflective layer 106 is surely lowered.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to make it possible to form a reflective electrode made of a metal having a high reflectance without reducing the reflectance.

  In order to achieve the above object, according to the present invention, a semiconductor light emitting device is provided with a protective layer made of a nonmetal between a reflective electrode and a metal layer for wiring (cover electrode). Thereby, it becomes possible to prevent mutual diffusion of metals constituting the reflective electrode and the cover electrode.

  Specifically, a semiconductor light emitting device according to the present invention includes a first conductive type first semiconductor layer, a second conductive type second semiconductor layer, and between the first semiconductor layer and the second semiconductor. An active layer formed on the first semiconductor layer, a reflective electrode made of a first metal that reflects light emitted from the active layer, and a first electrode in the reflective electrode. A protective layer made of a non-metal formed on the opposite surface of the semiconductor layer, and a second metal formed on the surface of the protective layer opposite to the reflective electrode and electrically connected to the reflective electrode And a cover electrode.

  According to the semiconductor light emitting device of the present invention, the protective layer made of a nonmetal is provided between the reflective electrode and the cover electrode, and the cover electrode is electrically connected to the reflective electrode. For this reason, since the protective layer made of a non-metal can more reliably prevent mutual diffusion between the first metal constituting the reflective electrode and the second metal constituting the cover electrode, the reflectance of light in the reflective electrode can be reduced. A decrease can be prevented. In addition, the nonmetal which comprises a protective layer means a dielectric material or a semiconductor.

  The semiconductor light emitting device of the present invention preferably further comprises a second conductivity type electrode formed on the surface of the second semiconductor layer opposite to the active layer. In this case, the reflective electrode formed in the first semiconductor layer and the second conductivity type electrode formed in the second semiconductor layer are formed so as to sandwich the active layer. The injected current flows only in a so-called vertical direction that is substantially perpendicular to the semiconductor layers of the first semiconductor layer, the active layer, and the second semiconductor layer. Thereby, the influence of the sheet resistance in the second semiconductor layer is eliminated, so that low voltage driving can be realized.

  In the semiconductor light emitting device of the present invention, the protective layer has an opening for electrically connecting the reflective electrode and the cover electrode, and the coverage of the protective layer in the region excluding the opening is 50% or more and Preferably it is less than 100%. If it does in this way, since the coverage of the protective layer in a reflective electrode can be made high with 50% or more, the reflectance of a reflective electrode can be kept high.

  In this case, the opening is preferably an opening groove provided in the peripheral edge of the protective layer. In this way, the reflective electrode can maintain a high reflectance at the central portion of the first semiconductor layer, and can stably obtain an electrical connection between the reflective electrode and the cover electrode.

  In this case, the opening is preferably a plurality of opening grooves provided in a lattice shape in the protective layer. If it does in this way, the electrical connection of a reflective electrode and a cover electrode can be taken uniformly, keeping the reflectance of a reflective electrode high.

  In this case, the opening is preferably a plurality of opening holes provided in the protective layer at intervals. If it does in this way, the electrical connection of a reflective electrode and a cover electrode can be taken stably and uniformly, keeping the reflectance of a reflective electrode high. In addition, since the protective layer is a continuous film except for the plurality of opening holes, the adhesion between the reflective electrode and the protective layer is improved, and the manufacturing yield is improved.

  In the semiconductor light emitting device of the present invention, the reflective electrode preferably contains silver (Ag), aluminum (Al), or rhodium (Rh) as a main component. Thus, when Ag, Al, or Rh having a high reflectance in the visible region to the ultraviolet region is used as the first metal in a single layer, the reflectance of the reflective electrode can be at least 60% or more.

  In the semiconductor light emitting device of the present invention, the thickness of the reflective electrode is preferably 50 nm or more. If it does in this way, since the emitted light from an active layer will be reflected efficiently, without permeate | transmitting a reflective electrode, the reflectance of a reflective electrode can be made high.

  The semiconductor light emitting device of the present invention preferably further includes a contact layer formed between the first semiconductor layer and the reflective electrode and in ohmic contact with the first semiconductor layer. Thus, the contact resistance of the reflective electrode with the first semiconductor layer is reduced, so that the operating voltage of the light-emitting device can be reduced. In addition, by providing the contact layer, the adhesion of the reflective electrode to the first semiconductor layer is improved, so that the reliability of the light-emitting device is improved.

  In this case, the contact layer preferably has a light-transmitting property with respect to light emitted from the active layer. In this way, even if the emitted light from the active layer passes through the contact layer, the emitted light reaches the reflective electrode without being greatly attenuated, so that the reflectance can be kept high throughout the reflective electrode. Here, translucency means that most of the light incident on the contact layer is transmitted without being absorbed by the contact layer.

  In this case, the thickness of the contact layer is preferably 20 nm or less. In this case, even when the contact layer has absorption with respect to the emission wavelength, that is, when the emission light is absorbed, the contact layer can transmit light by reducing the thickness of the contact layer to 20 nm or less. The rate can be increased. Therefore, the reflectance can be kept high over the entire reflective electrode.

  In the semiconductor light emitting device of the present invention, when the first semiconductor layer is a p-type layer, the contact layer is made of nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh), silver (Ag). ), Indium tin oxide (ITO), zinc oxide (ZnO) or nickel oxide (NiO). In this way, it is possible to form a reflective electrode having good ohmic contact with the first semiconductor layer whose conductivity type is p-type.

  In the semiconductor light emitting device of the present invention, when the first semiconductor layer is an n-type layer, the contact layer is made of titanium (Ti), aluminum (Al), palladium (Pd), nickel (Ni), silicon (Si) ), Indium (In), indium tin oxide (ITO) or zinc oxide (ZnO). In this way, it is possible to form a reflective electrode having good ohmic contact with the first semiconductor layer whose conductivity type is n-type.

  In the semiconductor light emitting device of the present invention, the protective layer preferably contains an oxide or a nitride.

In this case, the protective layer includes silicon oxide (SiO ₂ ), magnesium oxide (MgO), beryllium oxide (BeO), aluminum oxide (Al ₂ O ₃ ), zinc oxide (ZnO), boron nitride (BN), and aluminum nitride. It is preferable to include (AlN), gallium nitride (GaN), or silicon nitride (Si ₃ N ₄ ). Since these materials are stable with respect to heat treatment, mutual diffusion between the first metal and the second metal can be prevented, and a reflective electrode in which the reflectance does not decrease can be realized.

  In the semiconductor light emitting device of the present invention, the protective layer preferably contains silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), or silicon carbide (SiC). In this case, since it is stable against heat treatment, it is possible to realize a reflective electrode in which the reflectance does not decrease. In addition, when the protective layer is formed of these semiconductors, the protective layer itself serves as a current path, so that the operating voltage can be reduced.

  In the semiconductor light emitting device of the present invention, the thermal conductivity of the protective layer is preferably 10 W / m · K or more. If it does in this way, since the heat dissipation of a protective layer becomes favorable, a reflective electrode can be formed, without producing deterioration of the heat dissipation by a protective layer. As a result, the output of the semiconductor light emitting device can be increased.

  In the semiconductor light emitting device of the present invention, the cover electrode preferably contains gold (Au). In this way, long-term stability can be obtained for the cover electrode, and the yield in mounting can be improved even when wire bonding or the like is applied to the cover electrode.

  A method of manufacturing a semiconductor light emitting device according to the present invention includes: a step of sequentially forming a first conductive type first semiconductor layer, an active layer, and a second conductive type second semiconductor layer on a substrate; Forming a reflective electrode made of a first metal on the semiconductor layer, forming a protective layer made of a non-metal on the reflective electrode, and forming an opening exposing the reflective electrode in the protective layer; And a step of forming a cover electrode made of the second metal and in contact with the reflective electrode through the opening on the protective layer in which the opening is formed.

  According to the method for manufacturing a semiconductor light emitting device of the present invention, a protective layer made of a nonmetal is formed on the reflective electrode, and an opening for exposing the reflective electrode is formed in the formed protective layer. Subsequently, a cover electrode made of a second metal that is in contact with the reflective electrode through the opening is formed on the protective layer in which the opening is formed. Thereby, the semiconductor light emitting device of the present invention can be obtained.

  In the method for manufacturing a semiconductor light emitting device of the present invention, in the step of forming the protective layer, the protective layer is preferably formed on the exposed surface of the second semiconductor layer and the side surfaces of the light emitting layer and the first semiconductor layer. In this case, since the protective layer for protecting the reflective electrode and the protective layer for protecting the light emitting device itself can be formed at the same time, a more reliable semiconductor light emitting device can be realized by a simple process.

  Moreover, it is preferable that the manufacturing method of the semiconductor light-emitting device of the present invention further includes a step of performing a heat treatment at 300 ° C. or higher after the step of forming the protective layer. In this way, the contact resistance of the connection portion between the reflective electrode and the first semiconductor layer is reduced. Furthermore, even when such a heat treatment is performed, mutual diffusion between the first metal and the second metal is prevented by the protective layer formed between the reflective electrode and the cover electrode.

  According to the semiconductor light emitting device and the method for manufacturing the same according to the present invention, it is possible to realize a semiconductor light emitting device including a reflective electrode that prevents a decrease in reflectance due to heat treatment, has a high reflectance, and has a low contact resistance.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1A shows a semiconductor light emitting device according to a first embodiment of the present invention, which shows a planar configuration of the LED device, and FIG. 1B is a cross-sectional configuration taken along line Ib-Ib in FIG. Is shown.

As shown in FIG. 1A and FIG. 1B, the semiconductor light emitting device according to the first embodiment has translucency with respect to light emitted from the light emitting device, for example, sapphire (single crystal Al). ₂ O ₃ ) having a planar dimension of 350 μm × 350 μm, an n-type semiconductor layer 11 sequentially formed on the main surface of the substrate 10 by epitaxial growth, an active layer 12 made of multiple quantum wells, p Type semiconductor layer 13.

On the p-type semiconductor layer 13, a peripheral portion is formed inward by 10 μm from the end face of the p-type semiconductor layer 13, a reflective electrode 14 made of silver (Ag) having a thickness of 100 nm, and a silicon oxide having a thickness of 200 nm. A protective layer 15 made of (SiO ₂ ) and having an opening groove 15a that exposes the reflective electrode 14 at the peripheral portion and a first cover electrode 16 for mounting made of gold (Au) having a thickness of 300 nm are sequentially formed. Yes. On the region where a part of the n-type semiconductor layer 11 is exposed by etching, an n-side electrode 17 in ohmic contact with the n-type semiconductor layer 11 and a second cover electrode 18 made of Au are sequentially formed. . Here, the planar dimension of the n-side electrode 17 is 75 μm × 75 μm.

  The active layer 12 has a multiple quantum well structure or a superlattice structure made of, for example, InGaN. In the active layer 12, aluminum (Al) may be added to the barrier layer portion in the quantum well structure or the superlattice structure.

The n-type semiconductor layer 11 is made of n-type GaN with a thickness of 4 μm, and the p-type semiconductor layer 13 is undoped Al _0.15 Ga _0.85 N with a thickness of 30 nm and p-type Al _0.3 Ga _0.7 N with a thickness of 10 nm. And p-type Al _0.15 Ga _0.85 N with a thickness of 30 nm, p-type GaN with a thickness of 15 nm, and p ⁺ -type GaN with a thickness of 5 nm.

  An opening groove 15 a having a width of 5 μm is formed in the peripheral portion of the protective layer 15, and a part of the first cover electrode 16 comes into contact with the reflection electrode 14 through the opening groove 15 a, whereby the reflection electrode 14 and the first electrode 15. The cover electrode 16 is electrically connected. In this case, the coverage of the protective layer 15 with respect to the reflective electrode 14 is 93%.

  The semiconductor light emitting device according to this embodiment is a so-called flip-chip type LED device in which the first cover electrode 16 and the second cover electrode 18 are mounted to face a mounting substrate (submount) (not shown).

  Hereinafter, a method for manufacturing the LED device configured as described above will be described.

  First, a buffer layer (not shown) made of GaN having a thickness of 200 nm is formed on the main surface of a substrate 10 made of sapphire by metal organic chemical vapor deposition (MOCVD), and made of n-type GaN. An active layer 12 and a p-type semiconductor layer 13 having a multiple quantum well structure in which well layers made of, for example, InGaN and barrier layers made of GaN are alternately stacked are sequentially epitaxially grown.

Next, a mask forming film (not shown) made of nickel having a thickness of 300 nm is formed on the entire surface of the p-type semiconductor layer 13 by an electron beam (EB) vapor deposition method. By a lithography method and a wet etching method using a nitric acid solution, a mask film having an opening in an upper portion of the n-side electrode formation region in the mask formation film is obtained. Subsequently, using the formed mask film, for example, by dry etching using ECR (Electron Cyclotron Resonance) plasma using chlorine (Cl ₂ ) gas, the upper portions of the p-type semiconductor layer 13, the active layer 12, and the n-type semiconductor layer 11 are formed. Then, an n-side electrode formation region is formed in a part of the n-type semiconductor layer 11.

  Next, the mask film is removed with a nitric acid solution, and then a first resist pattern (not shown) that opens the reflective electrode formation region is formed on the p-type semiconductor layer 13 by lithography. On the resist pattern, an Ag film having a thickness of 100 nm is formed by EB vapor deposition. Subsequently, a reflective electrode 14 made of Ag is formed on the p-type semiconductor layer 13 by a so-called lift-off method in which the first resist pattern is removed together with the Ag film deposited on the resist pattern. Here, the reflective electrode 14 is preferably formed so as to cover almost the entire upper surface of the p-type semiconductor layer 13.

Next, a silicon oxide (SiO ₂ ) film having a thickness of 200 nm is formed on the entire surface by plasma CVD (plasma-chemical vapor deposition). Subsequently, a second resist pattern (not shown) having an opening that exposes the formation region of the opening groove 15a and the outside of the reflective electrode 14 is formed on the formed silicon oxide film, and the formed second oxide film is formed. Using the resist pattern as a mask, the silicon oxide film is wet etched with a buffered hydrofluoric acid solution. Thereafter, by removing the second resist pattern, the protective layer 15 having the opening groove 15a formed in the peripheral edge portion is obtained.

  Next, the first cover electrode 16 made of Au having a thickness of 300 nm is selectively formed on the protective layer 15 while filling the opening groove 15a formed in the protective layer 15 by lithography, EB vapor deposition, and lift-off. To form. Here, since the flip-chip type LED device is connected to the submount by the first cover electrode 16 and the second cover electrode 18, the first cover electrode 16 is provided so as to improve the heat dissipation of the LED device. It is preferable that the reflective electrode 14 and the protective layer 15 have substantially the same size (planar area).

Next, in order to reduce the contact resistance of the formed reflective electrode 14 with the p-type semiconductor layer 13, a first heat treatment is performed for 30 minutes in a nitrogen atmosphere at a temperature of 600 ° C. By this first heat treatment, the contact resistance of the reflective electrode 14 can realize a good ohmic contact with an order of 10 ⁻⁴ Ω · cm ² .

Next, titanium (Ti) / aluminum (Al) / nickel (Ni) is applied from below onto the n-side electrode formation region where a part of the n-type semiconductor layer 11 is exposed by lithography, EB vapor deposition, and lift-off. A metal laminated film made of / gold (Au) is sequentially formed to form the n-side electrode 17. Here, the thickness of each metal film constituting the n-side electrode 17 is 30 nm, 180 nm, 50 nm, and 150 nm in order. Thereafter, in order to reduce the contact resistance of the formed n-side electrode 17, a second heat treatment is performed in a nitrogen atmosphere at a temperature of 600 ° C. for 1 minute. By this second heat treatment, the contact resistance of the n-side electrode 17 can realize a good ohmic contact with an order of 10 ⁻⁶ Ω · cm ² .

  Next, a second cover electrode 18 made of Au having a thickness of 300 nm is selectively formed on the n-side electrode 17 by lithography, EB vapor deposition, and lift-off. The second cover electrode 18 may be formed in the same process as the first cover electrode 16.

  Through the above steps, a flip-chip type LED device is obtained in which the emitted light emitted from the active layer 12 is reflected to the substrate 10 side by the reflective electrode 14 and the emitted light is extracted from the transparent substrate 10 side. .

  In the first embodiment, silver (Ag) is used as the reflective electrode 14 formed on the p-type semiconductor layer 13, but instead of Ag, aluminum (Al) or rhodium (Rh) is used. A material having a high light reflectance in the ultraviolet region to the visible region can be used.

  FIG. 2 shows the wavelength dependence (calculated value) of the reflectance of the single-layer metal film in the air. Ag, Al, and Rh have higher reflectivity than nickel (Ni) or platinum (Pt) used for the p-side electrode of the conventional gallium nitride semiconductor, and are promising as a material for the reflective electrode 14. Among these, Ag is most suitable as a reflective electrode provided in the p-type semiconductor layer because it can achieve both high reflectance and low contact resistance. Although the thickness of the reflective electrode 14 is 100 nm here, it is not limited to this thickness.

  FIG. 3 shows the film thickness dependence (calculated value) of the light transmittance when the wavelength of the reflective electrode 14 made of Ag is 400 nm and 477 nm. As can be seen from FIG. 3, when the thickness of the reflective electrode 14 is reduced, a decrease in reflectance (increase in transmittance) of the reflective electrode 14 cannot be ignored. Therefore, the thickness of the reflective electrode 14 is 50 nm or more. Is more preferable and 80 nm or more is more preferable.

  Thus, according to the first embodiment, since the protective layer 15 made of silicon oxide, which is a non-metal, here, an insulator, is formed between the reflective electrode 14 and the first cover electrode 16, The Ag and the first cover electrode 16 constituting the reflective electrode 14 are formed by heat treatment at a temperature of about 600 ° C. for reducing the contact resistance in the electrode 14 and heat treatment at a temperature of about 300 ° C. when the LED device is mounted. It is possible to prevent the reflectance of the reflective electrode 14 from being lowered due to mutual diffusion with the constituent Au. Accordingly, it is possible to realize a high-power LED device having the reflective electrode 14 that can maintain the desired reflectance even when subjected to heat treatment at 300 ° C. or higher.

FIG. 4 shows how the reflectance of light having a wavelength of 400 nm changes before and after heat treatment in reflective electrodes having various layer structures. As shown in FIG. 4, from the left of the graph, a single layer film made of Ag, a laminated film made of Ag / Au, a laminated film made of Ag / Pt / Au, and a laminated film made of Ag / SiO ₂ / Au, respectively. On the other hand, the reflectance before and after heat treatment at a temperature of 600 ° C. was measured by irradiating light having a wavelength of 400 nm. Here, Ag is for comparison and is a single-layer reflective electrode, Ag / Au is a reflective electrode and a cover electrode without a protective layer, and Ag / Pt / Au is Pt between the reflective electrode and the cover electrode. This is a conventional configuration in which a protective layer made of (metal) is provided, and Ag / SiO ₂ / Au is a configuration of the present invention in which a protective layer made of non-metallic SiO ₂ is provided between the reflective electrode and the cover electrode. .

As can be seen from FIG. 4, in the case of an Ag / Au film and an Ag / Pt / Au film, the reflectance of the reflective electrode made of Ag is significantly lowered by performing heat treatment. On the other hand, in the case of the Ag / SiO ₂ / Au film according to the present invention, it is understood that the reflectance is hardly lowered even after the heat treatment, and the high reflectance is maintained. A reflective electrode made of only Ag does not have a significant decrease in reflectance even after heat treatment, but is impractical because Ag itself is easily oxidized and has poor durability.

  In Patent Document 1 described above, a reflection electrode and a wiring metal layer (= cover electrode) are used as a diffusion prevention layer (= protective layer) for preventing diffusion of metals such as platinum (Pt), palladium (Pd), and nickel (Ni). ) Is described. According to FIG. 4, platinum has a greatly reduced reflectivity after heat treatment at a temperature of 600 ° C., and does not function as a diffusion preventing layer. The same applies to the case where nickel (Ni) is used for the diffusion prevention layer.

  In the first embodiment, the reflective electrode 14 and the first cover electrode 16 are electrically connected by providing the opening groove 15a in the peripheral portion of the protective layer 15 made of nonmetal. The electrical connection location is not limited to the peripheral edge of the protective layer 15.

  For example, as shown in the first modification of FIGS. 5A and 5B, lattice-shaped opening grooves 15b each having a width of 5 μm may be provided on the entire surface of the protective layer 15. In this case, the coverage of the protective layer 15 with respect to the reflective electrode 14 is 80%. As a result, the number of electrical connection portions between the reflective electrode 14 and the first cover electrode 16 is increased, and the first cover electrode 16 is uniformly connected over the entire surface of the reflective electrode 14. On the other hand, the current can be uniformly injected.

  As a second modification, for example, as shown in FIGS. 6 (a) and 6 (b), a plurality of apertures 15c spaced in the form of dots each having a diameter of 10 μm are formed on the entire surface of the protective layer 15. May be provided. In this case, the coverage of the protective layer 15 with respect to the reflective electrode 14 is 95%. In this way, the protective layer 15 can be formed as a continuous pattern that is not divided by the opening grooves 15a and 15b. As a result, it is possible to inject current uniformly into the reflective electrode 14 and to prevent a decrease in adhesion of the protective layer 15 to the reflective electrode 14. It goes without saying that the coverage of the protective layer 15 can be changed by changing the formation density of the opening hole 15 c with respect to the opening diameter or the area of the protective layer 15.

  Moreover, since all of the opening grooves 15a and 15b and the opening hole 15c are portions that are not protected by the protective layer 15 for the reflective electrode 14, the reflectance is lowered by the heat treatment. Therefore, it is preferable that the opening areas of the opening grooves 15a and 15b and the opening hole 15c are as small as possible. Specifically, the coverage of the protective layer 15 with respect to the reflective electrode 14 is preferably 50% or more and less than 100%, more preferably 80% or more and less than 100%.

In the first embodiment, silicon oxide (SiO ₂ ) is used as the constituent material of the protective layer 15, but other dielectric materials and semiconductor materials can be used instead of silicon oxide. For example, metal oxides such as magnesium oxide (MgO), beryllium oxide (BeO), aluminum oxide (Al ₂ O ₃ ), or zinc oxide (ZnO), boron nitride (BN), aluminum nitride (AlN), gallium nitride (GaN) ) Or a nitride such as silicon nitride (Si ₃ N ₄ ), or a semiconductor such as silicon (Si), gallium arsenide (GaAs), gallium nitride (GaN), or silicon carbide (SiC).

  As described above, since the first cover electrode 16 is electrically connected to the reflective electrode 14 through the portion filled in the opening groove 15a provided in the protective layer 15, the electrical conductivity of the protective layer 15 is It may be low. Therefore, regarding the electrical conductivity, the range of selection of the material constituting the protective layer 15 is widened except for a material having a high conductivity such as a metal. That is, the material of the protective layer 15 may be selected based on whether or not it has high thermal stability.

  In addition, since most of the reflective electrode 14 is covered with the protective layer 15 made of a nonmetal, the thermal conductivity of the protective layer 15 greatly affects the heat dissipation of the entire LED device. For this reason, the material for forming the protective layer 15 is preferably a material having high thermal conductivity.

FIG. 7 shows thermal conductivities of various dielectric materials and semiconductor materials. As can be seen from FIG. 7, the silicon oxide (SiO ₂ ) used for the protective layer 15 in the first embodiment has a low thermal conductivity of about 1.5 W / m · K, which is not necessarily preferable in terms of heat dissipation. I can't say that. That is, in the case of an LED device that handles a large current, there is a risk that the characteristics may be deteriorated due to thermal saturation.

  Therefore, in the case where a material having a relatively low thermal conductivity such as silicon oxide is used for the protective layer acid 15, in order to reduce the thermal resistance of the entire LED device and improve the heat dissipation of the LED device, the protective layer 15 A method of reducing the thickness of the film can be considered. For example, when the protective layer 15 is formed from silicon oxide, the thickness of the protective layer 15 is preferably set to 200 nm or less.

  In contrast, aluminum nitride (AlN), boron nitride (BN), beryllium oxide (BeO), silicon carbide (SiC), and the like have a thermal conductivity as high as that of the metal, so that the heat dissipation of the protective layer 15 is improved. Very good in terms of being raised. Here, a material having a thermal conductivity of at least 10 W / m · K or more is preferable from the viewpoint of heat dissipation.

  In addition, when a semiconductor such as Si is used for the protective layer 15, the electrical conductivity of the protective layer 15 can be increased by doping impurities at a high concentration. For this reason, since the protective layer 15 itself also functions as a current path, the operating voltage of the LED device can be reduced.

  Further, as in the first and second modifications of the present embodiment, the opening groove 15b and the opening hole 15c are formed in the entire protective layer 15, thereby forming the opening groove 15b in the first cover electrode 16 and the like. Since the filled part (connection part) functions as a heat dissipation path, the heat dissipation of the entire LED device is further improved.

  In the first embodiment, gold (Au) is used for the first cover electrode 16 and the second cover electrode 18, but is not limited to gold. However, in addition to the stability and oxidation resistance as a cover electrode (wiring metal), the cover electrodes 16 and 18 preferably contain gold (Au) from the viewpoint of adhesion to the wire during wire bonding.

  Each cover electrode 16 and 18 may be a laminated film instead of a single layer film. For example, when a Ti / Au laminated film having a titanium (Ti) film in contact with the protective layer 15 is used, the adhesion with the protective layer 15 is improved, so that a more stable LED device can be obtained.

Moreover, in 1st Embodiment, although sapphire was used for the board | substrate 10, it is not restricted to sapphire. That is, other substrates such as gallium nitride (GaN) or gallium oxide (Ga ₂ O ₃ ) can be used as long as the substrate has a property of transmitting light emitted from the active layer 12.

  In the first embodiment, the n-type semiconductor layer 11 is formed on the substrate 10 and the p-type semiconductor layer 13 is formed on the active layer 12. However, the n-type semiconductor layer 11 and the p-type semiconductor layer are formed. The mutual conductivity types with 13 may be interchanged. In this case, the reflective electrode 14, the protective layer 15, and the first cover electrode 16 are formed on the n-type semiconductor layer.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

  FIG. 8A shows a semiconductor light emitting device according to the second embodiment of the present invention, which shows a planar configuration of the LED device, and FIG. 8B is a cross-sectional configuration taken along line VIIIb-VIIIb of FIG. Is shown. In FIG. 8A and FIG. 8B, the same components as those in FIG.

  As shown in FIG. 8B, in the semiconductor light emitting device according to the second embodiment, the reflective electrode 22 is formed on the contact layer 20 made of nickel (Ni) with a thickness of 0.5 nm and the reflective electrode 22 thereon. It has a laminated structure with a reflective layer 21 made of silver (Ag) having a thickness of 100 nm.

That is, in the second embodiment, a thin film made of Ni is used as the contact layer 20 with the p ⁺ -type GaN layer located above the p-type semiconductor layer 13 in the reflective electrode 22. Thus, by forming the contact layer 20 between the p-type semiconductor layer 13 and the reflective layer 21 of the reflective electrode 22, the adhesion of the reflective layer 21 to the p-type semiconductor layer 13 is improved. As a result, since the reflective electrode 22 can obtain a good ohmic contact with the p-type semiconductor layer 13, an LED device with high reliability can be realized. In order to sufficiently function the reflective function of the reflective layer 21 made of Ag, the thickness of the contact layer 20 needs to be thin enough to transmit the emitted light sufficiently.

  FIG. 9 shows the Ni film thickness dependence of the reflectance of light having a wavelength of 400 nm in the reflective electrode 22 having the contact layer 20 made of Ni. In FIG. 9, it can be seen that the reflectance of the reflective electrode 22 before the heat treatment increases as the thickness of the Ni film decreases, as indicated by the diamond marks ◆. Similarly, the reflectance after heat treatment indicated by a triangle mark ▲ also tends to increase as the Ni film thickness decreases. However, when the Ni film thickness is 0, that is, when the Ni film is not provided, the heat treatment is performed. It can be seen that the later reflectance is slightly reduced. This is because, when the contact layer 20 made of Ni is not provided, the adhesion of the reflective layer 21 made of Ag to the p-type semiconductor layer 13 is low, and the heat treatment causes the interface between the reflective electrode 22 and the p-type semiconductor layer 13. This is due to floating. Therefore, from the viewpoint of the light transmittance in the contact layer 20 and the adhesion between the p-type semiconductor layer 13, the thickness of the contact layer 20 is preferably 2 nm or less, and most preferably 0.5 nm. Such a contact layer 20 can be formed on the p-type semiconductor layer 13 by, for example, EB vapor deposition after epitaxial growth of the p-type semiconductor layer 13.

  In the second embodiment, nickel (Ni) is used as a constituent material of the contact layer 20, but a material capable of obtaining good ohmic contact with the p-type GaN layer can be used in addition to Ni. For example, platinum (Pt), palladium (Pd), rhodium (Rh), indium tin oxide (ITO), zinc oxide (ZnO), nickel oxide (NiO), or the like can be used. In addition, when aluminum (Al) or rhodium (Rh) is used for the reflective layer 21, silver (Ag) can be used as the contact layer 20.

  Further, when the light transmittance of the contact layer 20 with respect to the wavelength of the emitted light is low, it is preferable to reduce the thickness of the contact layer 20 as in the case of Ni. In the case where a conductive material having translucency such as ITO is used for the contact layer 20, it is not always necessary to reduce the thickness of the contact layer 20.

  In the second embodiment, the n-type semiconductor layer 11 is formed on the substrate 10 and the p-type semiconductor layer 13 is formed on the active layer 12. However, the n-type semiconductor layer 11, the p-type semiconductor layer 13, The conduction types of each other may be interchanged. In this case, titanium (Ti), aluminum (Al), palladium (Pd), nickel (Ni), silicon (Si) is used as the contact layer 20 from the viewpoint of adhesion to the n-type semiconductor layer and reduction of contact resistance. Indium (In), indium tin oxide (ITO), zinc oxide (ZnO), or the like is preferable.

  As described above, according to the second embodiment, the expected reflectance of the reflective electrode 22 can be maintained and the adhesion between the reflective electrode 22 and the p-type semiconductor layer or the n-type semiconductor layer can be improved. Therefore, it is possible to realize a flip-chip type high-power LED device having a longer life and higher reliability.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.

  FIG. 10A is a semiconductor light emitting device according to the third embodiment of the present invention, and shows a planar configuration of the LED device, and FIG. 10B is a cross-sectional configuration taken along line Xb-Xb in FIG. Is shown. In FIG. 10, the same components as those in FIG.

  As shown in FIG. 10A and FIG. 10B, in the third embodiment, the protective layer 15 formed between the reflective electrode 14 and the first cover electrode 16 is formed with the n-type semiconductor layer 11 and The exposed portion of the p-type semiconductor layer 13 is also covered to form a passivation film that protects the LED device itself.

  Further, unlike the first embodiment, a heat treatment for reducing the contact resistance between the reflective electrode 14 and the n-side electrode 17, for example, a heat treatment for 1 minute in a nitrogen atmosphere at a temperature of 600 ° C. is simultaneously performed.

  As a result, the step of newly forming a passivation film can be reduced, and the two heat treatment steps can be reduced to one, thereby simplifying the manufacturing process. Furthermore, the protective layer 15 is formed not only on the upper side of the reflective electrode 14 but also on the entire exposed surface of the semiconductor layer, thereby suppressing migration of electrodes such as the reflective electrode 14 and the n-side electrode 17 due to the operating current of the LED device. become able to. For this reason, it is possible to prevent defects caused by migration. Moreover, it is possible to prevent defects caused by impurities or the like adhering to the side surface of the LED device.

  As described above, according to the third embodiment, the desired reflectance of the reflective electrode 14 is maintained, and the flip-chip type high-power LED that can simplify the process, has a longer life, and has high reliability. A device can be realized.

In the third embodiment, silicon oxide is used for the protective layer 15 also serving as a passivation film. However, instead of silicon oxide, magnesium oxide (MgO), beryllium oxide (BeO), aluminum oxide (alumina: Al ₂ O ₃ ), zinc oxide (ZnO), boron nitride (BN), aluminum nitride (AlN), or silicon nitride (Si 3). Also in the third embodiment, the n-type semiconductor layer 11 and the p-type semiconductor layer 13 are mutually connected. The conduction type may be switched.

(Fourth embodiment)
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.

  FIG. 11A is a semiconductor light emitting device according to the fourth embodiment of the present invention, and shows a planar configuration of the LED device, and FIG. 11B is a cross-sectional configuration taken along line XIb-XIb in FIG. Is shown. In FIG. 11, the same components as those in FIG.

  As shown in FIGS. 11A and 11B, the semiconductor light emitting device according to the fourth embodiment has a diameter of about 70 μm on the surface of the n-type semiconductor layer 11 opposite to the active layer 12. An n-side electrode 30 and a second cover electrode 31 are formed.

  A holding film 32 made of gold (Au) having a thickness of 50 μm is formed on the surface of the first cover electrode 16 opposite to the protective layer 15. Therefore, in the fourth embodiment, the substrate for epitaxially growing the n-type semiconductor layer 11 and the like is removed.

  Thus, in the LED device according to the fourth embodiment, the reflective electrode 14 formed on the p-type semiconductor layer 13 and the n-side electrode 30 formed on the n-type semiconductor layer 11 sandwich the active layer 12. As a so-called vertical device, the current injected into the LED device flows in a direction substantially perpendicular to the semiconductor layers of the p-type semiconductor layer 13, the active layer 12, and the n-type semiconductor layer 11. It is formed. Since the vertical device is not affected by the sheet resistance in the n-type semiconductor layer 11, low voltage driving can be realized.

  Hereinafter, a method for manufacturing the LED device configured as described above will be described.

  First, on the main surface of a substrate (not shown) made of sapphire by MOCVD, a buffer layer (not shown) made of GaN, an n-type semiconductor layer 11 made of n-type GaN, for example, a well layer made of InGaN, The active layer 12 and the p-type semiconductor layer 13 having a multiple quantum well structure in which barrier layers made of GaN are alternately stacked are sequentially epitaxially grown. Thereafter, the region except the element formation portion in the epitaxially grown semiconductor layer is removed by dry etching.

  Next, a reflective film 14 made of Ag having a thickness of 100 nm is formed on the p-type semiconductor layer 13 by lithography, EB vapor deposition, and lift-off. Here, the reflective electrode 14 is preferably formed so as to cover almost the entire upper surface of the p-type semiconductor layer 13.

Next, a protective layer 15 made of silicon oxide (SiO ₂ ) having a thickness of 200 nm is formed on the formed reflective electrode 14 by plasma CVD. Subsequently, wet etching is selectively performed on the protective layer 15 to form an opening groove 15 a that exposes the peripheral edge of the reflective electrode 14 in the protective layer 15.

  Next, a first cover electrode 16 made of Au having a thickness of 300 nm is formed on the protective layer 15 by EB vapor deposition so as to fill the opening groove 15a formed in the protective layer 15.

  Next, in order to reduce the contact resistance between the reflective electrode 14 and the p-type semiconductor layer 13, a heat treatment is performed for 30 minutes in a nitrogen atmosphere at a temperature of 600 ° C.

  Next, a holding film 32 made of Au plating having a thickness of 50 μm is formed on the first cover electrode 16 by a plating method using the first cover electrode 16 as an underlayer for Au plating.

  Next, the n-type semiconductor layer 11 is irradiated with a third harmonic (third harmonic) laser beam of YAG (yttrium aluminum garnet) having a wavelength of 355 nm through a substrate made of sapphire. The substrate is peeled from the n-type semiconductor layer 11 by melting the interface portion with the substrate.

  Next, an n-side electrode 30 made of Ti / Al / Ni / Au sequentially formed from the n-type semiconductor layer 11 side is formed on the surface opposite to the active layer 12 in the n-type semiconductor layer 11 from which the substrate has been peeled off. Form. Here, the thicknesses of the respective metal films constituting the n-side electrode 30 are 30 nm, 180 nm, 50 nm, and 150 nm in order. Thereafter, in order to reduce the contact resistance of the formed n-side electrode 30, heat treatment is performed for 1 minute in a nitrogen atmosphere at a temperature of 600 ° C.

  Next, a second cover electrode 32 made of Au having a thickness of 300 nm is selectively formed on the n-side electrode 30 by lithography, EB vapor deposition, and lift-off.

  Through the above steps, a vertical LED device is obtained in which the emitted light emitted from the active layer 12 is reflected by the reflective electrode 14 toward the n-side electrode 30 to extract the emitted light to the outside.

  As described above, the LED device according to the fourth embodiment is a vertical LED in which the substrate for epitaxial growth is removed and the n-side electrode 30 is formed on the opposite side of the reflective electrode 14 with respect to the active layer 12. Device. Such a vertical LED device differs from a flip-chip LED device in that current does not flow in the n-type semiconductor layer 11 in a direction parallel to the active layer 12 (lateral direction), so that the element resistance is reduced. be able to. As a result, the operating voltage of the device can be reduced.

  The vertical LED device according to the fourth embodiment is compared not only on the substrate peeling step but also on the reflective electrode 14 side, that is, on the first cover electrode 16 in order to facilitate handling of the device after peeling. In particular, a holding film 32 made of Au having a large thickness is provided. For this reason, it is inevitable that another metal layer other than the first cover electrode 16 is formed on the reflective electrode 14. In addition, because of the structure of the device, it is necessary to form the holding film 32 before the n-side electrode 30 is formed, and thus heat treatment with the reflective electrode 14 formed is essential.

  Due to such process restrictions, mutual diffusion between the reflective electrode 14 and other metal layers due to heat treatment or the like is a concern. However, in the fourth embodiment, the protective layer 15 made of a non-metal is formed between the reflective electrode 14 and the first cover electrode 16, whereby Ag constituting the reflective electrode 14 and the first cover electrode. 16 and Au constituting the holding film 32 can be prevented from interdiffusion, so that even a vertical LED device can improve the reliability of the vertical LED device.

  In the fourth embodiment, Au plating is used as a constituent material of the holding film 32. However, a holding substrate made of silicon (Si), tungsten copper (CuW), or the like can be used. In this case, it is necessary to bond the first cover electrode 16 and the holding substrate using a mixed crystal solder material made of gold tin (AuSn) or the like. In addition, since the holding film 32 functions as a mount portion of the LED device, a material having high thermal conductivity is preferable.

  In the fourth embodiment, the substrate is peeled from the n-type semiconductor layer 11 using laser light, but other methods that do not use laser light may be used for peeling the substrate. For example, silicon (Si) may be used for the epitaxial growth substrate, and after forming the holding film 32 by the bonding process described above, the growth substrate made of Si may be peeled off by wet etching or gas etching.

  Also in the fourth embodiment, the conductivity types of the n-type semiconductor layer 11 and the p-type semiconductor layer 13 may be interchanged.

  As described above, according to the fourth embodiment, it is possible to realize a high-output vertical LED device with high reliability that operates at a lower voltage while maintaining the desired reflectance of the reflective electrode 14.

  In each of the second, third, and fourth embodiments, as shown in each modification of the first embodiment, the opening shape of the opening groove 15a of the protective layer 15 may be a lattice shape or a dot shape. it can.

  In each of the third and fourth embodiments, a configuration in which the reflective electrode 14 includes a contact layer can be used as shown in the second embodiment.

  The present invention can realize a semiconductor light-emitting device including a reflective electrode that prevents a decrease in reflectance due to heat treatment, has a high reflectance, and has a low contact resistance. For example, an excitation light source for a headlamp of an automobile or a white LED device for illumination It is useful as a blue LED device, an ultraviolet LED device, and the like that are expected to have a high output and a long lifetime.

(A) And (b) shows the semiconductor light-emitting device concerning the 1st Embodiment of this invention, (a) is a top view, (b) is sectional drawing in the Ib-Ib line | wire of (a). . It is a graph which shows the wavelength dependence (calculated value) of the reflectance of the single layer metal film in the air. It is a graph which shows the film thickness dependence of the light transmittance in the reflective electrode (Ag) used for the semiconductor light-emitting device concerning the 1st Embodiment of this invention. It is a graph which shows the change of the reflectance of the light whose wavelength is 400 nm before and behind heat processing of the reflective electrode used for the semiconductor light-emitting device concerning the 1st embodiment of the present invention with a comparative example. (A) And (b) shows the semiconductor light-emitting device concerning the 1st modification of the 1st Embodiment of this invention, (a) is a top view, (b) is the Vb-Vb line | wire of (a). FIG. (A) And (b) shows the semiconductor light-emitting device concerning the 2nd modification of the 1st Embodiment of this invention, (a) is a top view, (b) is VIb-VIb line | wire of (a). FIG. It is a table | surface which shows the heat conductivity of the material used for the protective layer used for the semiconductor light-emitting device concerning the 1st Embodiment of this invention. (A) And (b) shows the semiconductor light-emitting device concerning the 2nd Embodiment of this invention, (a) is a top view, (b) is sectional drawing in the VIIIb-VIIIb line | wire of (a). . It is a graph which shows the film thickness dependence of the Ni film | membrane of the reflectance of the light whose wavelength of the reflective electrode used for the semiconductor light-emitting device which concerns on the 2nd Embodiment of this invention is 400 nm. (A) And (b) shows the semiconductor light-emitting device concerning the 3rd Embodiment of this invention, (a) is a top view, (b) is sectional drawing in the Xb-Xb line | wire of (a). . (A) And (b) shows the semiconductor light-emitting device concerning the 4th Embodiment of this invention, (a) is a top view, (b) is sectional drawing in the XIb-XIb line | wire of (a). . It is sectional drawing which shows the conventional semiconductor light-emitting device.

Explanation of symbols

10 substrate 11 n-type semiconductor layer 12 active layer 13 p-type semiconductor layer 14 reflective electrode 15 protective layer 15a opening groove 15b opening groove (lattice shape)
15c Open hole (dot shape)
16 1st cover electrode 17 n side electrode (2nd conductivity type electrode)
18 Second cover electrode 20 Contact layer 21 Reflective layer 22 Reflective electrode 30 n-side electrode (second conductivity type electrode)
31 Second cover electrode 32 Holding film

Claims (21)

A first semiconductor layer of a first conductivity type;
A second semiconductor layer of a second conductivity type;
An active layer formed between the first semiconductor layer and the second semiconductor;
A reflective electrode made of a first metal that is formed on a surface of the first semiconductor layer opposite to the active layer and reflects light emitted from the active layer;
A protective layer made of a nonmetal formed on a surface of the reflective electrode opposite to the first semiconductor layer;
A semiconductor light emitting device comprising: a cover electrode made of a second metal formed on a surface of the protective layer opposite to the reflective electrode and electrically connected to the reflective electrode.   The semiconductor light emitting device according to claim 1, further comprising a second conductivity type electrode formed on a surface of the second semiconductor layer opposite to the active layer. The protective layer has an opening for electrically connecting the reflective electrode and the cover electrode,
3. The semiconductor light emitting device according to claim 1, wherein a coverage ratio of the region excluding the opening in the protective layer with respect to the reflective electrode is 50% or more and less than 100%.   4. The semiconductor light emitting device according to claim 3, wherein the opening is an opening groove provided in a peripheral portion of the protective layer.   The semiconductor light emitting device according to claim 3, wherein the opening is a plurality of opening grooves provided in a lattice shape in the protective layer.   The semiconductor light emitting device according to claim 3, wherein the opening is a plurality of opening holes provided in the protective layer at intervals.   The semiconductor light emitting device according to claim 1, wherein the reflective electrode contains silver, aluminum, or rhodium as a main component.   The semiconductor light-emitting device according to claim 1, wherein a thickness of the reflective electrode is 50 nm or more.   The semiconductor light emitting device according to claim 1, further comprising a contact layer formed between the first semiconductor layer and the reflective electrode and in ohmic contact with the first semiconductor layer. .   The semiconductor light-emitting device according to claim 9, wherein the contact layer has a light-transmitting property with respect to light emitted from the active layer.   The thickness of the said contact layer is 20 nm or less, The semiconductor light-emitting device of Claim 9 or 10 characterized by the above-mentioned.   The first semiconductor layer is a p-type layer, and the contact layer includes nickel, platinum, palladium, rhodium, silver, indium tin oxide (ITO), zinc oxide, or nickel oxide. The semiconductor light-emitting device of any one of 9-11.   10. The first semiconductor layer is an n-type layer, and the contact layer includes titanium, aluminum, palladium, nickel, silicon, indium, indium tin oxide (ITO), or zinc oxide. The semiconductor light-emitting device of any one of -11.   The semiconductor light-emitting device according to claim 1, wherein the protective layer includes an oxide or a nitride.   The semiconductor light emitting device according to claim 14, wherein the protective layer includes silicon oxide, magnesium oxide, beryllium oxide, aluminum oxide, zinc oxide, boron nitride, aluminum nitride, gallium nitride, or silicon nitride.   The semiconductor light emitting device according to claim 1, wherein the protective layer includes silicon, gallium arsenide, gallium nitride, or silicon carbide.   The semiconductor light-emitting device according to claim 1, wherein the protective layer has a thermal conductivity of 10 W / m · K or more.   The semiconductor light-emitting device according to claim 1, wherein the cover electrode includes gold. Sequentially forming a first conductive type first semiconductor layer, an active layer, and a second conductive type second semiconductor layer on a substrate;
Forming a reflective electrode made of a first metal on the second semiconductor layer;
Forming a protective layer made of a non-metal on the reflective electrode;
Forming an opening exposing the reflective electrode in the protective layer;
Forming a cover electrode made of a second metal and in contact with the reflective electrode through the opening on the protective layer in which the opening is formed. .   20. The protective layer according to claim 19, wherein in the step of forming the protective layer, the protective layer is also formed on an exposed surface of the second semiconductor layer and side surfaces of the light emitting layer and the first semiconductor layer. A method for manufacturing a semiconductor light emitting device.   21. The method of manufacturing a semiconductor light emitting device according to claim 19, further comprising a step of performing the heat treatment at 300 [deg.] C. or higher after the step of forming the protective layer.

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