Roughened high refractive index layer/LED for high light extraction

• US 20070018183A1
• Filed: 07/21/2005
• Published: 01/25/2007
• Est. Priority Date: 07/21/2005
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Nakamura, Shuji, Denbaars, Steven
• Granted Patent: US 8,674,375 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

A light emitting diode (LED) includes a p-type layer of material, an n-type layer of material and an active layer between the p-type layer and the n-type layer. A roughened layer of transparent material is adjacent one of the p-type layer of material and the n-type layer of material. The roughened layer of transparent material has a refractive index close to or substantially the same as the refractive index of the material adjacent the layer of transparent material, and may be a transparent oxide material or a transparent conducting material. An additional layer of conductive material may be between the roughened layer and the n-type or p-type layer.

Claims

1. A light emitting diode (LED) comprising:

a p-type layer of material;

an n-type layer of material;

an active layer between the p-type layer and the n-type layer; and

a roughened layer of transparent material adjacent one of the p-type layer of material and the n-type layer of material.

2. The LED of claim 1 wherein the roughened layer of transparent material has a refractive index substantially the same as the refractive index of the material adjacent the layer of transparent material.

3. The LED of claim 2 wherein the transparent material has a refractive index±

0.3 of the refractive index of the material adjacent to the transparent material.

4. The LED of claim 1 wherein the transparent material comprises at least one of ZnO, ZnS, MgO, In₂O₃, CdS, TiO₂, PbO, ZnSnO and indium tin oxide (ITO).

5. The LED of claim 1 wherein the transparent material comprises a transparent oxide material.

6. The LED of claim 5 wherein the transparent oxide material comprises at least one of ZnO, MgO, In₂O₃, TiO₂, PbO, ZnSnO, NiO and indium tin oxide (ITO).

7. The LED of claim 1 wherein the transparent material comprises a transparent conducting material.

8. The LED of claim 7 wherein the transparent conducting material comprises a transparent conducting oxide.

9. The LED of claim 8 wherein the transparent oxide material comprises at least one of ZnO, In₂O₃ and indium tin oxide (ITO).

10. A light emitting diode (LED) comprising:

a p-type layer of material;

an n-type layer of material;

an active layer between the p-type layer and the n-type layer;

a layer of transparent conducting material adjacent one of the p-type layer of material and the n-type layer of material; and

a roughened layer of transparent material adjacent the transparent conducting layer.

11. The LED of claim 10 wherein the transparent material comprises a material different from the transparent conducting material.

12. The LED of claim 11 wherein the transparent material is more transparent than the transparent conducting material.

13. The LED of claim 10 wherein the transparent conducting material compress a transparent conducting oxide.

14. The LED of claim 10 wherein the transparent conducting material has a refractive index substantially the same as the refractive index of the p-type or n-type material adjacent the transparent conducting layer.

15. The LED of claim 10 wherein the transparent material adjacent the transparent conducting layer has a refractive index substantially the same as the refractive index of the p-type or n-type material adjacent the transparent conducting layer.

16. A light emitting diode (LED) comprising:

a p-type layer of material;

an n-type layer of material;

an active layer between the p-type layer and the n-type layer;

a layer of metallic conducting material adjacent one of the p-type layer of material and the n-type layer of material; and

a roughened layer of transparent material adjacent the layer of metallic material.

17. The LED of claim 16 wherein the roughened layer of transparent material has a refractive index substantially the same as the refractive index of the material adjacent the layer of metallic conducting material.

18. The LED of claim 17 wherein the transparent material has a refractive index±

0.3 the refractive index of the material adjacent the layer of metallic conducting material.

19. A light emitting diode formed by a process comprising:

growing a base LED structure comprising a p-type layer of material, a n-type layer of material and an active layer between the p-type layer and the n-type layer;

depositing a layer of transparent material adjacent one of the p-type layer of material and the n-type layer of material; and

roughening the layer of transparent material.

20. The process of claim 19 wherein the growing and depositing are done using the same technique.

21. The process of claim 20 wherein the technique comprises metalorganic chemical vapor deposition (MOCVD).

22. The process of claim 19 wherein the base LED structure is grown p-side up on a substrate and the layer of transparent material is deposited adjacent the p-type layer of material.

23. The process of claim 22 wherein the transparent material is a transparent conducting material, and further comprising forming a p-contact adjacent the layer of transparent conducting material.

24. The process of claim 19 wherein the base LED structure is grown p-side up on a substrate, and further comprising:

forming a p-contact adjacent the p-type layer of material;

removing the substrate; and

flip mounting the LED structure p-side down on a submount;

wherein the layer of transparent material is deposited adjacent the n-type layer of material.

25. The process of claim 24 wherein the transparent material is a transparent conducting material, and further comprising forming an n-contact adjacent the layer of transparent conducting material.

26. A light emitting diode formed by a process comprising:

growing a base LED structure comprising a p-type layer of material, a n-type layer of material and an active layer between the p-type layer and the n-type layer;

depositing a layer of transparent conducting material adjacent one of the p-type layer of material and the n-type layer of material;

depositing a layer of transparent material adjacent the layer of transparent conducting material; and

roughening the layer of transparent material.

27. The process of claim 26 wherein the growing and depositing are done using the same technique.

28. The process of claim 27 wherein the technique comprises metalorganic chemical vapor deposition (MOCVD).

29. The process of claim 26 wherein the base LED structure is grown p-side up on a substrate and the layer of transparent conducting material is deposited adjacent the p-type layer of material.

30. The process of claim 29 further comprising:

removing a portion of the layer of transparent material to expose a portion of the layer of transparent conducting material; and

forming a p-contact adjacent the layer of transparent conducting material.

31. The process of claim 26 wherein the base LED structure is grown p-side up on a substrate, and further comprising:

forming a p-contact adjacent the p-type layer of material;

removing the substrate; and

flip mounting the LED structure p-side down on a submount.

32. The process of claim 31 wherein the layer of transparent conducting material is deposited adjacent the n-type layer of material, and further comprising:

removing a portion of the layer of transparent material to expose a portion of the layer of transparent conducting material; and

forming an n-contact adjacent the layer of transparent conducting material.

33. A light emitting diode formed by a process comprising:

growing a base LED structure comprising a p-type layer of material, a n-type layer of material and an active layer between the p-type layer and the n-type layer;

depositing a layer of metallic material adjacent one of the p-type layer of material and the n-type layer of material;

depositing a layer of transparent material adjacent the layer of metallic material; and

roughening the layer of transparent material.

34. The process of claim 33 wherein the growing and depositing are done using the same technique.

35. The process of claim 34 wherein the technique comprises metalorganic chemical vapor deposition (MOCVD).

36. The process of claim 33 wherein the base LED structure is grown p-side up on a substrate and the layer of metallic material is deposited adjacent the p-type layer of material.

37. The process of claim 36 further comprising:

removing a portion of the layer of transparent material to expose a portion of the layer of metallic material; and

forming a p-contact adjacent the layer of metallic material.

38. The process of claim 33 wherein the base LED structure is grown p-side up on a substrate, and further comprising:

forming a p-contact adjacent the p-type layer of material;

removing the substrate; and

flip mounting the LED structure p-side down on a submount.

39. The process of claim 38 wherein the layer of metallic material is deposited adjacent the n-type layer of material, and further comprising:

removing a portion of the layer of transparent material to expose a portion of the layer of metallic material; and

forming an n-contact adjacent the layer of metallic material.