Light emitting device

• US 7,489,068 B2
• Filed: 01/06/2006
• Issued: 02/10/2009
• Est. Priority Date: 01/25/2005
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: Epistar Corporation
• Inventors: Hsieh, Min-Hsun, Peng, Wei-Chih, Hsu, Ta-Cheng, Lee, Ya-Ju
• Primary Examiner(s): Patel; Vip
• Application Number:
  US11/326,750
• Publication Number:
  US 20060163595A1
• Time in Patent Office: 1,131 Days
• Field of Search: 313/116, 313/498, 313/506
• US Class Current: 313/116
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers

Abstract

A light emitting device having a transparent substrate, a light emitting stack, and a transparent adhesive layer is provided. The light emitting stack is disposed above the transparent substrate and comprises a diffusing surface. The transparent adhesive layer is disposed between the transparent substrate and the diffusing surface of the light emitting stack; an index of refraction of the light emitting stack is different from that of the transparent adhesive layer.

Claims

1. A light emitting device, comprising:

a transparent substrate;

a light emitting stack having a first diffusing surface above the transparent substrate; and

a transparent adhesive layer between the transparent substrate and the first diffusing surface, wherein an index of refraction of the light emitting stack is different from that of the transparent adhesive layer.

2. The light emitting device according to claim 1, wherein the transparent substrate comprises a material selected from the group consisting of GaP, SiC, Al₂O₃, and glass.

3. The light emitting device according to claim 1, wherein the transparent adhesive layer comprises a material selected from the group consisting of polyimide, benzocyclobutene (BCB), prefluorocyclobutane (PFCB), and indium tin oxide.

4. The light emitting device according to claim 1, wherein the first diffusing surface comprises a rough surface.

5. The light emitting device according to claim 4, wherein the rough surface comprises a plurality of micro protrusions.

6. The light-emitting device according to claim 5, wherein the micro protrusions have a shape selected from the group consisting of semi-sphere, pyramid, pyramid polygon, and combinations thereof.

7. The light emitting device according to claim 4, wherein the rough surface comprises a convex-concave surface.

8. The light emitting device according to claim 1, wherein the light emitting stack comprises:

a first semiconductor layer above the substrate and having the first diffusing surface;

a light emitting layer on a portion of the first semiconductor layer; and

a second semiconductor layer on the light emitting layer.

9. The light emitting device according to claim 8, wherein the second semiconductor layer has a second diffusing surface.

10. The light emitting device according to claim 8, further comprising a first electrode and a second electrode, wherein the first electrode is on the first semiconductor layer where the tight emitting layer is not disposed thereon, and the second electrode is on the second semiconductor layer.

11. The light emitting device according to claim 10, further comprising a first transparent conductive layer between the first electrode and the first semiconductor layer.

12. The light emitting device according to claim 11, wherein the first transparent conductive layer comprises a material selected from the group consisting of indium tin oxide, cadmium tin oxide, antimony tin oxide, zinc aluminum oxide, and zinc tin oxide.

13. The light emitting device according to claim 1, further comprising a first reaction layer and a second reaction layer, wherein the first reaction layer is between the transparent substrate and the transparent adhesive layer, and the second reaction layer between the transparent adhesive layer and the light emitting stack.

14. The light emitting device according to claim 13, wherein the first reaction layer comprises a material selected from the group consisting of SiN_X, Ti, and Cr.

15. The light emitting device according to claim 13, wherein the second reaction layer comprises a material selected from the group consisting of SiN_X, Ti, and Cr.

16. The light emitting device according to claim 13, wherein at least one of the first reaction layer and the second reaction layer is conductive.

17. The light emitting device according to claim 13, wherein the first diffusing surface comprises a plurality of micro protrusions, and the second reaction layer is in ohmic contact with the first reaction layer with the existence of the protrusions penetrating through the transparent adhesive layer.

18. The light emitting device according to claim 17, wherein the micro protrusions have a shape selected from the group consisting of semi-sphere, pyramid, pyramid polygon, and combinations thereof.

19. The light emitting device according to claim 13, wherein the first diffusing surface comprises a convex-concave surface, and the second reaction layer is in ohmic contact with the first reaction layer with the existence of a convex part of the convex-concave surface penetrating through the transparent adhesive layer.

20. The light emitting device according to claim 1, wherein the light emitting stack comprises:

a first semiconductor layer above the substrate and having the first diffusing surface;

a light emitting layer on the first semiconductor layer; and

a second semiconductor layer on the light emitting layer.

21. The light-emitting device according to claim 20, wherein the transparent substrate is conductive.

22. The light emitting device according to claim 20, wherein the second semiconductor layer has a second diffusing surface.

23. The light emitting device according to claim 20, wherein the transparent adhesive layer is a conductive adhesive layer and the transparent conductive adhesive layer comprises a material selected from the group consisting of intrinsically conductive polymer and polymer having conductive material distributed therein.

24. The light emitting device according to claim 23, wherein the polymer having conductive material distributed therein is selected from the group consisting of polyimide, benzocyclobutene (BCB), and prefluorocyclobutane (PFCB).

25. The light emitting device according to claim 23, wherein the conductive material comprises a material selected from the group consisting of indium tin oxide, cadmium tin oxide, antimony tine oxide, zinc oxide, zinc tin oxide, Au, and Ni/Au.

26. The light emitting device according to claim 20, further comprising a first electrode and a second electrode, wherein the first electrode is on the second semiconductor layer, and the second electrode is under the transparent substrate.

27. The light emitting device according to claim 26, further comprising a transparent conductive layer between the second semiconductor layer and the first electrode.

28. The light emitting device according to claim 27, wherein the transparent conductive layer comprises a material selected from the group consisting of indium tin oxide, cadmium tin oxide, antimony tin oxide, zinc aluminum oxide, and zinc tin oxide.