Light-emitting device having a patterned surface
A light-emitting device comprises a substrate having a top surface and a plurality of patterned units protruding from the top surface; and a light-emitting stack formed on the substrate and having an active layer with a first surface substantially parallel to the top surface, wherein one of the plurality of patterned units comprises a plurality of connecting sides constituting a first polygon shape in a top view of the light-emitting device, wherein the one of the plurality of patterned units comprises a vertex and a plurality of inclined surfaces respectively extending from the plurality of connecting sides, the plurality of inclined surfaces commonly joining at the vertex in a cross-sectional view of the light-emitting device, the vertex being between the top surface of the substrate and the first surface of the active layer, and the plurality of inclined surfaces comprises a second polygon shape in the cross-sectional view of the light-emitting device.
1. A light-emitting device comprising:
a substrate having a top surface and a plurality of patterned units protruding from the top surface of the substrate; and
a light-emitting stack formed on the substrate and having an active layer with a first surface substantially parallel to the top surface of the substrate,
wherein each of the plurality of patterned units comprises a circular shape in a top view of the light-emitting device,
wherein each of the plurality of patterned units comprises a cross-section comprising a width and a depth smaller than the width.
2. The light-emitting device according to claim 1 , wherein the plurality of patterned units comprises two curves with different curvatures in a cross-sectional view of the light-emitting device.
3. The light-emitting device according to claim 1 , wherein the plurality of patterned units is not parallel to the first surface of the active layer.
4. The light-emitting device according to claim 1 , wherein the plurality of patterned units comprises a semicircle shape or an arc shape in the cross-sectional view of the light-emitting device.
5. The light-emitting device according to claim 1 , wherein the plurality of patterned units comprises a V-shape in the cross-sectional view of the light-emitting device.
6. The light-emitting device according to claim 1 , wherein one of the plurality of patterned units contacts with another one of the plurality of patterned units.
7. The light-emitting device according to claim 1 , wherein the plurality of patterned units comprises different diameters in a top view of the light-emitting device.
8. The light-emitting device according to claim 1 , wherein one of the plurality of patterned units comprises a mesa on a top surface of the one of the plurality of patterned units.
9. The light-emitting device according to claim 1 , wherein a total surface area of the mesa of the plurality of patterned units do not exceed 3% of a total area of the top surface of the substrate.
10. The light-emitting device according to claim 1 , wherein one of the plurality of patterned units comprises a vertex, a first inclined line segment and a second inclined line segment, the first inclined line segment and the second inclined line segment connect at the vertex in the cross-sectional view of the light-emitting device.
11. The light-emitting device according to claim 10 , wherein vertices of the plurality of patterned units constitute vertices of a triangular shape.
12. The light-emitting device according to claim 1 , wherein the substrate comprises GaP, sapphire, GaN, or AN.
13. A light-emitting device comprising:
a substrate having a top surface and a plurality of patterned units on the top surface, the plurality of patterned units comprising a same material as that of the substrate; and
a light-emitting stack formed on the substrate and having an active layer with a first surface substantially parallel to the top surface of the substrate,
wherein one of the plurality of patterned units comprises a plurality of connecting sides constituting a first polygon shape in a top view of the light-emitting device,
wherein the one of the plurality of patterned units comprises a vertex and a plurality of inclined surfaces respectively extending from the plurality of connecting sides, the plurality of inclined surfaces commonly joining at the vertex in a cross-sectional view of the light-emitting device, the vertex being between the top surface of the substrate and the first surface of the active layer, and the plurality of inclined surfaces comprises a second polygon shape in the cross-sectional view of the light-emitting device, and
wherein the plurality of inclined surfaces is substantially not parallel to the first surface of the active layer.
14. The light-emitting device according to claim 13 , wherein the substrate and the plurality of patterned units comprise sapphire.
15. The light-emitting device according to claim 13 , wherein the plurality of patterned units is disposed in a variable period.
16. The light-emitting device according to claim 13 , wherein the plurality of patterned units is periodically arranged on the substrate.
17. The light-emitting device according to claim 13 , further comprising an undoped semiconductor layer formed on the substrate and enclosing the plurality of patterned units.
18. The light-emitting device according to claim 13 , wherein one of the plurality of patterned units comprises a width and a depth smaller than the width.
19. The light-emitting device according to claim 13 , wherein the substrate comprises an area parallel to the first surface and the area is not greater than 10% of a total area of the substrate.
20. The light-emitting device according to claim 13 , wherein one of the plurality of patterned units contacts with another one of the plurality of patterned units.