Light emitting element, method of manufacturing the same, and semiconductor device having light emitting element

Abstract

An InGaN active layer is formed on a sapphire substrate. A p-side electrode is formed on the InGaN active layer to supply an electric current to this InGaN active layer. The p-side electrode includes {circle over (1)} an Ni layer for forming an ohmic contact with a p-GaN layer, {circle over (2)} an Mo layer having a barrier function of preventing diffusion of impurities, {circle over (3)} an Al layer as a high-reflection electrode, {circle over (4)} a Ti layer having a barrier function, and {circle over (5)} an Au layer for improving the contact with a submount on a lead frame. The p-side electrode having this five-layered structure realizes an ohmic contact and high reflectance at the same time.

What is claimed is:  
     
         1 . A light emitting element comprising: 
 a substrate;    a light emitting layer formed on said substrate to emit light; and    a first electrode contacting said light emitting layer,    wherein said first electrode comprises:    an ohmic layer in ohmic contact with said light emitting layer;    a first barrier layer formed on said ohmic layer to prevent diffusion of metal atoms; and    a light reflecting layer formed on said first barrier layer to reflect the light.    
     
     
         2 . The light emitting element according to  claim 1 , wherein said substrate is an insulating substrate.  
     
     
         3 . The light emitting element according to  claim 1 , wherein said substrate is a semiconductor substrate.  
     
     
         4 . The light emitting element according to  claim 3 , further comprising a second electrode contacting said semiconductor substrate.  
     
     
         5 . The light emitting element according to  claim 1 , wherein said light emitting layer comprises a light emitting diode.  
     
     
         6 . The light emitting element according to  claim 1 , wherein said light emitting layer comprises: 
 a first semiconductor layer of first conductivity type;    an active layer formed on said first semiconductor layer to emit the light; and    a second semiconductor layer of second conductivity type formed on said active layer.    
     
     
         7 . The light emitting element according to  claim 6 , wherein said first electrode contacts said second semiconductor layer.  
     
     
         8 . The light emitting element according to  claim 6 , further comprising a second electrode contacting said first semiconductor layer.  
     
     
         9 . The light emitting element according to  claim 1 , wherein the light is radiated from the back side of said substrate.  
     
     
         10 . The light emitting element according to  claim 1 , wherein the light reflected by said light reflecting layer travels to the back side of said substrate.  
     
     
         11 . The light emitting element according to  claim 1 , wherein said first barrier layer prevents diffusion of the metal atoms between said ohmic layer and said light reflecting layer.  
     
     
         12 . The light emitting element according to  claim 1 , wherein said first barrier layer is made of a high-melting metal.  
     
     
         13 . The light emitting element according to  claim 1 , wherein the thickness of said first barrier layer is not more than 10 nm.  
     
     
         14 . The light emitting element according to  claim 1 , wherein said ohmic layer is a member of the group consisting of a metal, selected from the group consisting of Ni, Pt, Mg, Zn, Be, Ag, Au, and Ge, and an alloy containing the metal.  
     
     
         15 . The light emitting element according to  claim 1 , wherein said first barrier layer is a member of the group consisting of a metal, selected from the group consisting of W, Mo, Pt, Ni, Ti, Pd, and V, and an alloy containing the metal.  
     
     
         16 . The light emitting element according to  claim 1 , wherein said light reflecting layer is a member of the group consisting of a metal, selected from the group consisting of Al and Ag, and an alloy containing the metal.  
     
     
         17 . The light emitting element according to  claim 1 , wherein said ohmic layer and said first barrier layer are made of the same material.  
     
     
         18 . The light emitting element according to  claim 17 , wherein the material of said ohmic layer and said first barrier layer is a member of the group consisting of a metal, selected from the group consisting of Ni and Pt, and an alloy containing the metal.  
     
     
         19 . The light emitting element according to  claim 1 , wherein said ohmic layer is made up of a plurality of islands arranged into arrays.  
     
     
         20 . The light emitting element according to  claim 19 , wherein 
 a portion of the light passes through said ohmic layer and said first barrier layer and is reflected by said light reflecting layer, and    another portion of the light passes only through said first barrier layer and is reflected by said light reflecting layer.    
     
     
         21 . The light emitting element according to  claim 1 , wherein said first electrode further comprises: 
 a second barrier layer formed on said light reflecting layer; and    an overcoat electrode for mounting formed on said second barrier layer.    
     
     
         22 . The light emitting element according to  claim 21 , wherein said second barrier layer is made of a high-melting metal.  
     
     
         23 . The light emitting element according to  claim 1 , wherein said first electrode is positioned in a central portion of said light emitting layer.  
     
     
         24 . The light emitting element according to  claim 8 , wherein said first electrode is positioned in a central portion of said light emitting layer, and said second electrode surrounds said first electrode.  
     
     
         25 . The light emitting element according to  claim 4 , wherein said second electrode is positioned on the edge of said semiconductor substrate.  
     
     
         26 . The light emitting element according to  claim 4 , wherein said second electrode comprises a plurality of portions, and said plurality of portions are arranged apart form each other on the back side of said semiconductor substrate.  
     
     
         27 . A light emitting element comprising: 
 a substrate;    a first semiconductor layer of first conductivity type formed on said substrate;    an active layer formed on said first semiconductor layer to emit light;    a second semiconductor layer of second conductivity type formed on said active layer;    a first electrode formed in a central portion of said second semiconductor layer and contacting said second semiconductor layer; and    a second electrode formed on the edge of said first semiconductor layer and contacting said first semiconductor layer.    
     
     
         28 . A light emitting element comprising: 
 a substrate;    a first semiconductor layer of first conductivity type formed on said substrate;    an active layer formed on said first semiconductor layer to emit light;    a second semiconductor layer of second conductivity type formed on said active layer;    a first electrode formed in a central portion of said second semiconductor layer and contacting said second semiconductor layer; and    a second electrode contacting said first semiconductor layer and surrounding said first electrode.    
     
     
         29 . A light emitting element comprising: 
 a transparent substrate;    a first semiconductor layer of first conductivity type formed on said transparent substrate;    an active layer formed on said first semiconductor layer to emit light;    a second semiconductor layer of second conductivity type formed on said active layer;    a first electrode contacting said second semiconductor layer;    a plurality of second electrodes contacting said transparent substrate; and    a plurality of light reflecting layers arranged between said plurality of second electrodes and contacting said transparent substrate.    
     
     
         30 . A light emitting element comprising: 
 a transparent substrate;    a first semiconductor layer of first conductivity type formed on said transparent substrate;    an active layer formed on said first semiconductor layer to emit light;    a second semiconductor layer of second conductivity type formed on said active layer;    a first electrode contacting said second semiconductor layer;    a second electrode contacting said transparent substrate; and    a light reflecting layer contacting said transparent substrate.    
     
     
         31 . The light emitting element according to  claim 30 , wherein said first semiconductor layer, said active layer, and said second semiconductor layer form a ridge-shaped member in a central portion of said transparent substrate.  
     
     
         32 . The light emitting element according to  claim 31 , further comprising: 
 a current limiting layer formed on said transparent substrate to cover side surfaces of said ridge-shaped member; and    a third semiconductor layer formed on said ridge-shaped member and said current limiting layer.    
     
     
         33 . The light emitting element according to  claim 32 , wherein said second electrode is positioned immediately below said ridge-shaped member.  
     
     
         34 . The light emitting element according to  claim 33 , wherein said light reflecting layer surrounds said second electrode.  
     
     
         35 . The light emitting element according to  claim 30 , wherein said light reflecting layer is made of a material selected from the group consisting of a metal and a material containing a metal.  
     
     
         36 . The light emitting element according to  claim 30 , wherein said light reflecting layer is made of a material selected from the group consisting of a dielectric substance and a material containing a dielectric substance.  
     
     
         37 . The light emitting element according to  claim 30 , wherein said light reflecting layer comprises a high-refractive-index layer whose refractive index to the light is higher than that of said transparent substrate, and a low-refractive-index layer whose refractive index to the light is lower than that of said high-refractive-index layer.  
     
     
         38 . The light emitting element according to  claim 30 , wherein said first semiconductor layer, said active layer, and said second semiconductor layer are members of the group consisting of a compound, selected from the group consisting of InP, GaP, AlP, and GaAs, and a mixed crystal containing the compound.  
     
     
         39 . A semiconductor device comprising: 
 a lead frame;    a submount on said lead frame;    a light emitting element on said submount; and    a resin covering said light emitting element,    wherein said light emitting element comprises:    a substrate;    a first semiconductor layer of first conductivity type formed on said substrate;    an active layer formed on said first semiconductor layer to emit light;    a second semiconductor layer of second conductivity type formed on said active layer;    a first electrode formed in a central portion of said second semiconductor layer and contacting said second semiconductor layer; and    a second electrode contacting said first semiconductor layer and surrounding said first electrode, and    said first electrode comprises:    an ohmic layer in ohmic contact with said second semiconductor layer;    a first barrier layer formed on said ohmic layer to prevent diffusion of metal atoms; and    a light reflecting layer formed on said first barrier layer to reflect the light.    
     
     
         40 . A semiconductor device comprising: 
 a lead frame;    a submount on said lead frame;    a light emitting element on said submount; and    a resin covering said light emitting element,    wherein said light emitting element comprises:    a transparent substrate;    a first semiconductor layer of first conductivity type formed on said transparent substrate;    an active layer formed on said first semiconductor layer to emit light;    a second semiconductor layer of second conductivity type formed on said active layer;    a first electrode contacting said second semiconductor layer;    a second electrode contacting said transparent substrate; and    a light reflecting layer contacting said transparent substrate.    
     
     
         41 . A manufacturing method of a light emitting element, comprising the steps of: 
 forming a first semiconductor layer of first conductivity type on a substrate;    forming an active layer on the first semiconductor layer;    forming a second semiconductor layer of second conductivity type on the active layer; and    forming a first electrode contacting the second semiconductor layer,    wherein the step of forming the first electrode comprises the steps of:    forming an ohmic layer on the second semiconductor layer;    forming an ohmic contact between the second semiconductor layer and the ohmic layer by first annealing;    forming a first barrier layer on the ohmic layer; and    forming, on the first barrier layer, a light reflecting layer having high reflectance to light generated in the active layer.    
     
     
         42 . The manufacturing method according to  claim 41 , further comprising the steps of: 
 forming a second barrier layer on the light reflecting layer;    forming an overcoat electrode for mounting on the second barrier layer; and    performing second annealing at a temperature lower than that of the first annealing.    
     
     
         43 . The manufacturing method according to  claim 41 , wherein said substrate is an insulating substrate.  
     
     
         44 . The manufacturing method according to  claim 41 , wherein said substrate is a semiconductor substrate.  
     
     
         45 . The manufacturing method according to  claim 44 , further comprising the step of forming a second electrode contacting the semiconductor substrate.  
     
     
         46 . The manufacturing method according to  claim 41 , further comprising a second electrode contacting the first semiconductor layer.  
     
     
         47 . The manufacturing method according to  claim 41 , wherein the first barrier layer prevents diffusion of metal atoms between the ohmic layer and the light reflecting layer.  
     
     
         48 . The manufacturing method according to  claim 41 , wherein the first barrier layer is made of a high-melting metal.  
     
     
         49 . The manufacturing method according to  claim 41 , wherein the thickness of the first barrier layer is not more than 10 nm.  
     
     
         50 . The manufacturing method according to  claim 41 , wherein the ohmic layer is a member of the group consisting of a metal, selected from the group consisting of Ni, Pt, Mg, Zn, Be, Ag, Au, and Ge, and an alloy containing the metal.  
     
     
         51 . The manufacturing method according to  claim 41 , wherein the first barrier layer is a member of the group consisting of a metal, selected from the group consisting of W, Mo, Pt, Ni, Ti, Pd, and V, and an alloy containing the metal.  
     
     
         52 . The manufacturing method according to  claim 41 , wherein the light reflecting layer is a member of the group consisting of a metal, selected from the group consisting of Al and Ag, and an alloy containing the metal.  
     
     
         53 . The manufacturing method according to  claim 41 , wherein the ohmic layer and the first barrier layer are made of the same material.  
     
     
         54 . The manufacturing method according to  claim 53 , wherein the material of the ohmic layer and the first barrier layer is a member of the group consisting of a metal, selected from the group consisting of Ni and Pt, and an alloy containing the metal.  
     
     
         55 . The manufacturing method according to  claim 41 , wherein the ohmic layer is made up of a plurality of islands arranged into arrays.  
     
     
         56 . The manufacturing method according to  claim 42 , wherein the second barrier layer is made of a high-melting metal.  
     
     
         57 . The manufacturing method according to  claim 41 , wherein the first electrode is positioned in a central portion of the second semiconductor layer.  
     
     
         58 . The manufacturing method according to  claim 46 , wherein the first electrode is positioned in a central portion of the second semiconductor layer, and the second electrode surrounds the first electrode.  
     
     
         59 . The manufacturing method according to  claim 45 , wherein the second electrode is positioned on the edge of the semiconductor substrate.  
     
     
         60 . The manufacturing method according to  claim 45 , wherein the second electrode comprises a plurality of portions, which are arranged apart from each other on the back side of the semiconductor substrate.