Light emitting devices having light coupling layers
View Patent ↗A light emitting device comprises a first layer of an n-type semiconductor material, a second layer of a p-type semiconductor material, and an active layer between the first layer and the second layer. A light coupling layer is disposed adjacent to one of the first layer and the second layer. In some cases, the light coupling layer is formed by roughening a buffer layer of the light emitting device. The light emitting device includes an electrode in electrical communication with one of the first layer and the second layer through a portion of the light coupling layer.
1. A method for forming a light emitting device, comprising:
(a) forming an aluminum-containing Group III-V semiconductor layer on a first substrate;
(b) forming a u-type gallium nitride layer on the aluminum-containing Group III-V semiconductor layer;
(c) forming an n-type Group III-V semiconductor layer on the u-type gallium nitride layer;
(d) forming an active layer on the n-type Group III-V semiconductor layer;
(e) forming a p-type Group III-V semiconductor layer on the active layer;
(f) providing a second substrate on the p-type Group III-V semiconductor layer;
(g) removing the first substrate to expose the aluminum-containing Group III-V semiconductor layer;
(h) roughening the aluminum-containing Group III-V semiconductor layer and the u-type gallium nitride layer to form a light coupling structure including the aluminum-containing Group III-V semiconductor layer and the u-type gallium nitride layer; and
(i) providing an electrode on a top surface of the roughened surface of the light coupling structure so that the electrode contacts the aluminum-containing Group III-V semiconductor layer and the u-type gallium nitride layer.
2. The method of claim 1 , wherein the aluminum-containing Group III-V semiconductor layer and the u-type gallium nitride layer are roughened with a chemical etchant.
3. The method of claim 1 , wherein the aluminum-containing Group III-V semiconductor layer and the u-type gallium nitride layer are roughened by ion sputtering.
4. The method of claim 1 , further comprising:
before (c) forming an n-type gallium nitride layer on the u-type gallium nitride layer,
wherein the n-type gallium nitride layer is roughened when the aluminum-containing Group III-V semiconductor layer and the u-type gallium nitride layer are roughened.
5. The method of claim 1 , further comprising:
before (c) forming an n-type gallium nitride layer on the u-type gallium nitride layer,
wherein the roughened surface of the light coupling structure includes the n-type gallium nitride layer, and
the electrode contacts the n-type gallium nitride layer.