Light-emitting device

1. A light-emitting device, comprising:

a substrate;

a semiconductor stack comprising a first type semiconductor layer, a second type semiconductor layer and an active layer formed between the first type semiconductor layer and the second type semiconductor layer, wherein the first type semiconductor layer comprises a top surface;

wherein the top surface is a non-planar roughened surface;

a bonding layer formed between the substrate and the semiconductor stack;

a plurality of recesses comprising a bottom surface lower than the non-planar roughened surface; and

a plurality of buried electrodes physically buried in and electrically connected to the first type semiconductor layer, wherein the plurality of buried electrodes comprising an upper surface is formed in the plurality of recesses respectively, and the upper surface of the buried electrode is lower than the top surface of the first type semiconductor layer.

2. The light-emitting device according to claim 1 , wherein the non-planar roughened surface has an average roughness greater than 0.05 μm.

3. The light-emitting device according to claim 1 , wherein the material of each of the plurality of buried electrodes comprises metal or metal alloy.

4. The light-emitting device according to claim 1 , wherein the material of the bonding layer comprises transparent materials.

5. The light-emitting device according to claim 1 , wherein the substrate is a transparent substrate.

6. A light-emitting device comprising:

a substrate;

a semiconductor stack comprising a first type semiconductor layer, a second type semiconductor layer and an active layer formed between the first type semiconductor layer and the second type semiconductor layer;

a bonding layer formed between the substrate and the semiconductor stack;

a plurality of buried electrodes physically buried in and electrically connected to the first type semiconductor layer;

a trench formed in the semiconductor stack, wherein the trench is filled with conductive material; and

a first electrode electrically connected to the first type semiconductor layer and a second electrode electrically connected to the second type semiconductor layer, wherein the plurality of buried electrodes and the first electrode arc electrically connected through the trench.

7. The light-emitting device according to claim 6 , further comprising a plurality of recesses formed in the first type semiconductor layer, wherein the first type semiconductor layer comprises a top surface and the plurality of recesses comprises a bottom surface lower than the top surface, the plurality of buried electrodes comprising an upper surface is formed in the plurality of recesses respectively.

8. The light-emitting device according to claim 7 , wherein the upper surface of the buried electrode is higher than the top surface of the first type semiconductor layer.

9. The light-emitting device according to claim 7 , wherein each of the plurality of buried electrodes comprises an embedded portion formed under the top surface of the first type semiconductor layer and an exposed portion formed above the top surface of the first type semiconductor layer.

10. The light-emitting device according to claim 9 , wherein the size of the embedded portion is larger than that of the exposed portion.

11. The light-emitting device according to claim 9 , wherein the size of the embedded portion is equal to that of the exposed portion.

12. The light-emitting device according to claim 9 , wherein the size of the embedded portion is smaller than that of the exposed portion.

13. The light-emitting device according to claim 6 , wherein the first type semiconductor layer comprises a top surface, and the top surface is a roughened surface.

14. The light-emitting device according to claim 13 , wherein an average roughness of the roughened surface is greater than 0.05 μm.

15. The light-emitting device according to claim 13 , wherein the plurality of buried electrodes comprises an upper surface lower than the roughened surface of the first type semiconductor layer.

16. The light-emitting device according to claim 13 , wherein the plurality of buried electrodes comprising an upper surface higher than the roughened surface of the first type semiconductor layer.

17. The light-emitting device according to claim 7 , wherein the upper surface of the buried electrode and the top surface of the first type semiconductor layer are substantially on the same plane.

18. The light-emitting device according to claim 7 , wherein the upper surface of the buried electrode is lower than the top surface of the first type semiconductor layer.

19. The light-emitting device according to claim 6 , wherein the material of each of the plurality of buried electrodes comprises metal or metal alloy.