Optoelectronic device and the manufacturing method thereof

1. An optoelectronic device, comprising:

a semiconductor stack having a first surface;

a contact layer having a first pattern on the first surface for ohmically contacting the semiconductor stack;

a void in the semiconductor stack and surrounding the contact layer; and

a mirror structure on the first surface and covering the contact layer;

wherein the first surface has a first portion which is not covered by the contact layer and a second portion covered by the contact layer, and the first portion is rougher than the second portion.

2. The optoelectronic device according to claim 1 , wherein the contact layer has a border and the void connects to the border.

3. The optoelectronic device according to claim 2 , wherein a cross section of the void is substantially a triangle.

4. The optoelectronic device according to claim 3 , wherein one corner of the triangle connects to the border.

5. The optoelectronic device according to claim 3 , wherein the triangle has two sides connecting to the first surface, and two angles respectively between the two sides and the first surface are different.

6. The optoelectronic device according to claim 3 , wherein a length of one side of the triangle is smaller than 2 μm.

7. The optoelectronic device according to claim 1 , wherein the void contains air.

8. The optoelectronic device according to claim 1 , wherein the first portion of the first surface has a first roughness (Ra) smaller than 0.5 μm.

9. The optoelectronic device according to claim 1 , wherein the mirror structure comprises a transparent layer having a second pattern on the semiconductor stack, a reflecting layer conformably covering the contact layer and the transparent layer.

10. The optoelectronic device according to claim 9 , wherein the second pattern is complementary to the first pattern.

11. The optoelectronic device according to claim 9 , wherein the void has a first reflective index R 1 , the transparent layer has a second reflective index R 2 , and R 1 <R 2 .

12. The optoelectronic device according to claim 9 , further comprises a barrier layer conformably covering the reflecting layer.

13. The optoelectronic device according to claim 12 , wherein the barrier layer comprises Ti, Pt, Au or the combination thereof.

14. The optoelectronic device according to claim 9 , wherein the reflecting layer comprises Ag, Au or Al.

15. The optoelectronic device according to claim 9 , wherein the transparent layer comprises SiN X , Al 2 O 3 , SiO x or MgF 2 .

16. The optoelectronic device according to claim 9 , wherein the transparent layer comprises indium tin oxide (ITO), cadmium tin oxide (CTO), antimony tin oxide, indium zinc oxide (IZO), zinc aluminum oxide (AZO), zinc tin oxide.

17. The optoelectronic device according to claim 9 , wherein the transparent layer has a thickness smaller than 2 μm.

18. The optoelectronic device according to claim 1 , wherein the contact layer comprises Ge, Be, Au or the combination thereof.

19. A method of manufacturing an optoelectronic device, comprising the steps of:

providing a semiconductor stack having a first surface, wherein the first surface has a first portion and a second portion;

forming a contact layer on the second portion of the first surface;

roughening the first portion of the first surface;

forming a void in the semiconductor stack and surrounding the contact layer; and

forming a mirror structure on the first surface to cover the contact layer;

wherein the step of forming the void and the step of roughening the second portion are at the same time.

20. The method of manufacturing an optoelectronic device according to the claim 19 , wherein the contact layer has a border and the void connects to the border.