Light emitting device with transparent conductive group-III nitride layer
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.
1. A method for manufacturing a light-emitting semiconductor device, the method comprising: depositing an n-type layer composed of a nitride of at least one group-III element; depositing a p-type layer over the n-type layer, the p-type layer composed of a nitride of at least one group-III element; and depositing a transparent, current spreading layer on the p-type layer, the transparent, current spreading layer being n-type and composed of a nitride of at least one group-III 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; and producing a current aperture stop between the transparent, current spreading layer and the p-type layer from a part of the p-type layer by effecting a diffusion of foreign atoms locally into the p-type layer to increase the local resistivity of said part of the p-type layer.
2. The method according to claim 1 , wherein the n-type layer is deposited using metal organic vapor phase epitaxy.
3. The method according to claim 1 , wherein as deposited the p-type layer has passivated dopants, the method further comprising activating said passivated dopants in at least a portion of the p-type layer.
4. The method according to claim 3 , wherein the passivated dopants are activated in said portion of the p-type layer by applying a local heat treatment.
5. The method according to claim 1 , wherein the current aperture stop has a resistivity amounting to at least 10 times a resistivity of the p-type layer.
6. The method according to claim 1 , wherein effecting the diffusion of the foreign atoms locally into the p-type layer comprises: depositing on the p-type 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 p-type layer by applying a heat treatment.
7. The method according to claim 1 , wherein effecting the diffusion of the foreign atoms locally into the p-type layer comprises: depositing on the p-type 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 p-type layer.
8. The method according to claim 1 , wherein the p-type layer is doped with Mg as a p-type dopant.
9. The method according to claim 1 , wherein the electrical conductivity of the transparent, current spreading layer exceeds the electrical conductivity of the p-type layer by at least a factor of 10.
10. The method according to claim 1 , wherein a point defect density in the transparent, current spreading layer is at least one of: above 5×10 19 /cm3; between 5×10 19 /cm3 and 1×10 21 /cm3; and between 5×10 19 /cm3 and 5×10 20 /cm3.
11. The method according to claim 1 , wherein the at least one group-III element is at least one of: Ga, Al and In.
12. The method according to claim 1 , wherein the n-type layer is doped n-type with at least one of Si, O and Ge.
13. The method according to claim 1 , wherein the transparent, current spreading layer is doped n-type with at least one of Si, O and Ge.
14. The method according to claim 1 , wherein the light-emitting semiconductor device is an edge emitting semiconductor device.
15. The method according to claim 14 , wherein the edge emitting semiconductor device is one of: an edge emitting laser diode, optical amplifier, a superluminescent diode and a light emitting diode.
16. The method according to claim 1 , wherein the light-emitting semiconductor device is one of a vertical cavity surface emitting laser and a resonant cavity light emitting diode.
17. The method according to claim 1 , wherein the p-type layer is deposited using metal organic vapor phase epitaxy and the transparent, current spreading layer is deposited using molecular beam epitaxy.
18. The method according to claim 1 , further comprising a non-intentionally doped layer arranged between the n-type layer and the p-type layer.