Light emitting device with transparent conductive group-iii nitride layer

Abstract

A group III-nitride semiconductor device comprises a light emitting semiconductor structure comprising a p-type layer and an n-type layer operable as a light emitting diode or laser. On top of the p-type layer there is arranged an n+ or n++-type layer of a group III-nitride, which is transparent to the light emitted from the underlying semiconductor structure and of sufficiently high electrical conductivity to provide lateral spreading of injection current for the light-emitting semiconductor structure.

What is claimed is: 
     
         1 . A device comprising:
 a light-emitting semiconductor structure operable to emit light and comprising a first layer, which is p-type and composed of a nitride of at least one group-III element, and a second layer, which is n-type and composed of a nitride of at least one group-III element; and   a transparent, current spreading layer of a nitride composed of at least one group-III element, which is transparent to light emitted from the light-emitting semiconductor structure and of sufficiently high electrical conductivity to provide lateral spreading of injection current for the light-emitting semiconductor structure within the transparent, current spreading layer.   
     
     
         2 . The device according to  claim 1 , wherein the electrical conductivity of the transparent, current spreading layer exceeds the electrical conductivity of the first layer by at least a factor of 10. 
     
     
         3 . The device according to  claim 1 , wherein the transparent, current spreading layer is n-type. 
     
     
         4 . The device according to  claim 1 , further comprising a current aperture stop defining a current aperture between a portion of the first layer and a portion of the transparent, current spreading layer. 
     
     
         5 . The device according to  claim 4 , wherein the current aperture stop has a resistivity of at least 10 times a resistivity of the first layer. 
     
     
         6 . The device according to  claim 4 , wherein the current aperture stop is composed of a nitride of at least one group-III element. 
     
     
         7 . The device according to  claim 1 , wherein the first layer is doped with Mg as a p-type dopant. 
     
     
         8 . The device according to  claim 1 , wherein a point defect density in the transparent, current spreading layer is at least one of: above 5·10 19 /cm 3 ; between 5-10 19 /cm 3  and 1·10 21 /cm 33 ; and between 5·10 19 /cm 3  and 5·10 20 /cm 3 . 
     
     
         9 . A method for manufacturing a device, the method comprising:
 producing a light-emitting semiconductor structure operable to emit light by depositing a first layer, which is p-type and composed of a nitride of at least one group-III element, and depositing a second layer, which is n-type and composed of a nitride of at least one group-III element; and   depositing a transparent, current spreading layer, which is n-type and composed of a nitride of at least one group-Ill element, the transparent, current spreading layer being configured to be transparent to light emitted from the light-emitting semiconductor structure and of sufficiently high electrical conductivity to provide lateral spreading of injection current for the light-emitting semiconductor structure within the transparent, current spreading layer.   
     
     
         10 . The method according to  claim 9 , wherein at least the first layer of the light-emitting semiconductor structure is deposited using metal organic vapor phase epitaxy, and wherein the transparent, current spreading layer is deposited using molecular beam epitaxy. 
     
     
         11 . The method according to  claim 9 , wherein as deposited the first layer has passivated dopants, the method further comprising activating said passivated dopants in at least a portion of the first layer. 
     
     
         12 . The method according to  claim 11 , wherein the passivated dopants are activated in said portion of the first layer by applying a local heat treatment. 
     
     
         13 . The method according to  claim 9 , further comprising producing a current aperture stop between the transparent, current spreading layer and die first layer so as to define a current aperture therebetween. 
     
     
         14 . The method according to  claim 13 , wherein the current aperture stop has a resistivity amounting to at least 10 times a resistivity of the first layer. 
     
     
         15 . The method according to  claim 13 , wherein the current aperture stop is produced from a part of the first layer by locally increasing the resistivity in said part of the first layer, wherein locally increasing the resistivity in said part of the first layer comprises effecting a diffusion of foreign atoms locally into the first layer. 
     
     
         16 . The method according to  claim 15 , wherein effecting the diffusion of the foreign atoms locally into the first layer comprises:
 depositing on the first layer, in a lateral area where the current aperture stop is to be produced, a diffusion-promoting mask containing the foreign atoms; and   effecting the diffusion of the foreign atoms into the first layer by applying a heat treatment.   
     
     
         17 . The method according to  claim 15 , wherein effecting the diffusion of the foreign atoms locally into the first layer comprises:
 depositing on the first layer, in a lateral area where the current aperture is to be produced, a diffusion-inhibiting mask; and   applying a plasma containing the foreign atoms to diffuse into the first layer.   
     
     
         18 . The method according to  claim 9 , wherein the first layer is doped with Mg as a p-type dopant. 
     
     
         19 . The method according to  claim 9 , wherein the electrical conductivity of the transparent, current spreading layer exceeds the electrical conductivity of the first layer by at least a factor of 10. 
     
     
         20 . The method according to  claim 9 , wherein a point defect density in the transparent, current spreading layer is at least one of: above 5·10 19 /cm 3 : between 5·10 19 /cm 3  and 1·10 21 /cm 33 ; and between 5·10 19 /cm 3  and 5·10 20 /cm 3 .