Light-emitting device
View Patent ↗A light-emitting device is provided. The light-emitting device comprises a light-emitting stack comprising a first semiconductor layer, a second semiconductor layer and an active layer between the first semiconductor layer and the second semiconductor layer. The light-emitting device further comprises a third semiconductor layer on the light-emitting stack and comprising a first sub-layer, a second sub-layer and a roughened surface, wherein the first sub-layer has the same composition as that of the second sub-layer, and the composition of the first sub-layer is with a different atomic ratio from that of the second sub-layer. A method for manufacturing the light-emitting device is also provided.
1. A light-emitting device, comprising:
a light-emitting stack comprising a first semiconductor layer, a second semiconductor layer and an active layer between the first semiconductor layer and the second semiconductor layer; and
a third semiconductor layer on the light-emitting stack and comprising a first sub-layer, a second sub-layer and a roughened surface, wherein the first sub-layer has the same composition as that of the second sub-layer, the composition of the first sub-layer is with a different atomic ratio from that of the second sub-layer, and the second sub-layer is farther from the light-emitting stack than the first sub-layer,
wherein a semiconductor material of the first sub-layer comprises (Al y Ga (1-y) ) 1-x In x P, a semiconductor material of the second sub-layer comprises (Al z Ga (1-z) ) 1-x In x P, wherein z is greater than y.
2. The light-emitting device according to claim 1 , wherein the third semiconductor layer further comprises a first portion and a second portion, wherein the second portion comprises the roughened surface.
3. The light-emitting device according to claim 2 , wherein the first portion has a first thickness t 1 , the second portion has a second thickness between 0.3*t 1 and 0.85*t 1 .
4. The light-emitting device according to claim 3 , wherein the first thickness is between 2000 nm and 4000 nm both inclusive.
5. The light-emitting device according to claim 2 , wherein the second portion substantially surrounds the first portion.
6. The light-emitting device according to claim 1 , wherein a difference between z and y is between 0.1 and 0.5 both inclusive.
7. The light-emitting device according to claim 1 , wherein 0≦x<1, 0.3≦y≦0.5, 0.5≦z≦0.7, and a difference between z and y is not less than 0.1.
8. The light-emitting device according to claim 1 , wherein 0≦x<1, 0.3≦y≦0.5, 0.4≦z≦0.7, wherein z is gradually decreased in a direction toward the light-emitting stack.
9. The light-emitting device according to claim 1 , wherein the second sub-layer is on the first sub-layer and comprises an upper face, and the roughened surface is between the light-emitting stack and the upper face.
10. The light-emitting device according to claim 9 , further comprising a first electrode on the upper surface of the first portion.
11. The light-emitting device according to claim 1 , wherein the second sub-layer has a thickness smaller than a thickness of the first sub-layer.
12. The light-emitting device according to claim 1 , wherein the roughened surface has an irregular surface texture.
13. The light-emitting device according to claim 1 , wherein one of the elements of the second sub-layer has an atomic percentage gradually changed toward the light-emitting stack.
14. The light-emitting device according to claim 1 , wherein 0≦x<1, 0.3≦y≦0.5, and 0.5≦z≦0.7.
15. The light-emitting device according to claim 1 , wherein z is gradually decreased in a direction toward the light-emitting stack.