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 each of the plurality of textured structures comprises a top portion having a first top-view shape, and a bottom portion parallel to the top portion and having a second top-view shape, wherein the first top-view shape comprises a circle or an ellipse, 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 each of the first periphery and the second periphery.
1. A light-emitting device, comprising:
a substrate comprising a boundary and a plurality of textured structures within the boundary, wherein the plurality of textured structures and the substrate are both composed of sapphire; and
a light-emitting stack overlaying the plurality of textured structures, 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 circle pattern in a top view, and wherein the one of the plurality of textured structures is constituted by a portion and sidewall portions formed inside a periphery of the portion, the sidewall portions intersect at one point without forming a flat portion in a cross-sectional view of the light-emitting device.
2. The light-emitting device according to claim 1 , wherein a cross-section of one of the sidewall portions is a curve.
3. The light-emitting device according to claim 1 , wherein a cross-section of one of the sidewall portions near the periphery is a curve.
4. The light-emitting device according to claim 1 , further comprising a semiconductor buffer layer directly formed on the substrate, wherein the semiconductor buffer layer comprises a III-nitride compound.
5. The light-emitting device according to claim 1 , wherein the light-emitting stack comprises a III-nitride compound.
6. The light-emitting device according to claim 1 , wherein the portion of the plurality of textured structures comprises a circle shape in a top view.
7. The light-emitting device according to claim 1 , wherein the plurality of textured structures are spaced apart from each other.
8. The light-emitting device according to claim 1 , wherein the sidewall portion comprises a sapphire R-plane.
9. The light-emitting device according to claim 1 , wherein a portion of the light-emitting stack is removed to expose the first conductivity type semiconductor layer.
10. The light-emitting device according to claim 9 , further comprising a first electrode formed on the exposed first conductivity type semiconductor layer, and a second electrode formed on the second conductivity type semiconductor layer.
11. The light-emitting device according to claim 10 , further comprising a reflecting layer on a lower surface of the substrate.
12. The light-emitting device according to claim 11 , wherein the reflecting layer comprises SiO 2 , Al 2 O 3 , SiN x or TiO 2 .