Light-emitting device having a patterned substrate and the method thereof

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 each of the plurality of textured structures comprises a top portion having a first top-view shape, a bottom portion parallel to the top portion and having a second top-view shape different from the first top-view shape, and three symmetric planes connecting the top portion and the bottom portion,

wherein the first top-view shape comprises a first periphery and the second top-view shape comprises a second periphery, the first periphery is enclosed by the second periphery, and various distances are between the first periphery and the second periphery.

2. The light-emitting device according to claim 1 , wherein the first top-view shape and the second top-view shape are different from each other.

3. The light-emitting device according to claim 1 , wherein at least one of the top portion and the bottom portion comprises a flat plane.

4. The light-emitting device according to claim 3 , wherein the flat plane comprises a sapphire C plane.

5. The light-emitting device according to claim 1 , wherein the three symmetric planes are sapphire R-planes.

6. The light-emitting device according to claim 1 , wherein a cross-section of the three symmetric planes near the top portion is a curve.

7. The light-emitting device according to claim 1 , wherein a cross-section of the three symmetric planes near the bottom portion is a curve.

8. The light-emitting device according to claim 1 , wherein a cross-section of the bottom portion is rounded.

9. The light-emitting device according to claim 1 , wherein the light-emitting stack comprises a III-nitride compound.

10. The light-emitting device according to claim 1 , further comprising a semiconductor buffer layer directly formed on the plurality of textured structures of the textured substrate, wherein the semiconductor buffer layer comprises a III-nitride compound.

11. The light-emitting device according to claim 1 , wherein the first top-view shape is located within the second top-view shape.

12. A light-emitting device, comprising:

a textured substrate comprising a boundary and a plurality of textured structures within the boundary, 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 is constituted by a bottom portion and three symmetric planes formed inside a periphery of the bottom portion, the at least three symmetric planes are inclined to intersect at one point and without forming a flat portion.

13. The light-emitting device according to claim 12 , wherein each of the plurality of textured structures comprises a top-view shape, the one point is enclosed by the top-view shape from a top view of the textured substrate, and the one point is symmetric to a periphery of the top-view shape.

14. The light-emitting device according to claim 12 , wherein an angle between adjacent two of the at least three symmetric planes is 120 degrees.

15. The light-emitting device according to claim 12 , wherein one of the three symmetric planes comprises a curved sidewall.

16. The light-emitting device according to claim 12 , further comprising a reflecting layer on a lower surface of the textured substrate.

17. The light-emitting device according to claim 16 , wherein the reflecting layer comprises SiO2, Al2O3, SiNx, or TiO2.