Light-emitting device having a patterned substrate and the method thereof
A light-emitting device comprises a textured substrate comprising a plurality of textured structures, wherein the textured structures and the textured substrate are both composed of sapphire; and a light-emitting stack overlaying the textured substrate, comprising a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer, wherein one of the plurality of textured structures comprises a top portion and a bottom portion, wherein a first distance between a first projection of the top portion on the bottom portion and the bottom portion at one side is different from a second distance between a second projection of the top portion on the bottom portion and the bottom portion at another side.
1. A light-emitting device, comprising:
a textured substrate comprising a plurality of textured structures, wherein the plurality of textured structures and the textured substrate are both composed of sapphire; and
a light-emitting stack overlaying the textured substrate, comprising a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer,
wherein one of the plurality of textured structures comprises a top portion and a bottom portion, wherein a first distance between a first projection of the top portion on the bottom portion and the bottom portion at one side is different from a second distance between a second projection of the top portion on the bottom portion and the bottom portion at another side.
2. The light-emitting device according to claim 1 , wherein the top portion comprises a top-view shape comprising a circle or an ellipse, and the bottom portion comprises a second top-view shape comprising a triangle.
3. The light-emitting device according to claim 1 , wherein the first distance is depicted from one point at the top portion to an apex at the bottom portion, and the second distance is depicted from another one point at the top portion to an edge at the bottom portion.
4. The light-emitting device according to claim 1 , wherein the bottom portion comprises a flat plane.
5. The light-emitting device according to claim 4 , wherein the flat plane comprises a sapphire C plane.
6. The light-emitting device according to claim 1 , further comprising a sidewall portion between the top portion and the bottom portion, wherein the sidewall portion comprises a straight sidewall portion.
7. The light-emitting device according to claim 6 , wherein the sidewall portion comprises a plurality of symmetric planes.
8. The light-emitting device according to claim 7 , wherein the sidewall portion comprises a plurality of symmetric sapphire R-planes.
9. The light-emitting device according to claim 6 , wherein a cross-section of the sidewall portion near the top portion is a curve.
10. The light-emitting device according to claim 6 , wherein a cross-section of the sidewall portion near the bottom portion is a curve.
11. The light-emitting device according to claim 2 , wherein the bottom portion comprises rounded corner.
12. The light-emitting device according to claim 1 , wherein the light-emitting stack comprises a III-nitride compound.
13. The light-emitting device according to claim 1 , further comprising a semiconductor buffer layer directly formed on the textured structures of the textured substrate, wherein the semiconductor buffer layer comprises a III-nitride compound.
14. The light-emitting device according to claim 2 , wherein the second top-view shape is located within the first top-view shape.
15. A light-emitting device, comprising:
a textured substrate comprising a boundary and a plurality of textured structures within the boundary, wherein the textured structures and the textured substrate are both composed of sapphire; and
a light-emitting stack overlaying the textured substrate, comprising a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer,
wherein in a top view of the light-emitting device, one of the plurality of textured structures comprises a first portion comprising a polygon like pattern and a second portion comprising a circular pattern or an elliptical pattern, wherein the polygon like pattern is enclosed by the circular pattern or the elliptical pattern.
16. The light-emitting device according to claim 15 , wherein the one of the plurality of textured structures comprises a plurality of planes connecting the first portion and the second portion.
17. The light-emitting device according to claim 16 , wherein the planes comprises sapphire R-planes.
18. The light-emitting device according to claim 16 , wherein a cross-section of one of the plurality of planes near the first portion or the second portion is a curve.
19. The light-emitting device according to claim 18 , wherein the cross-section of the one of the plurality of planes between the first portion and the second portion comprises a flat plane.
20. The light-emitting device according to claim 16 , wherein a cross-section of one of the plurality of planes comprises one end near the first portion and another end near the second portion, and the one end and the another end are curved.