Light-emitting devices having coplanar electrical contacts adjacent to a substrate surface opposite an active region and methods of forming the same

• US 7,714,345 B2
• Filed: 04/06/2004
• Issued: 05/11/2010
• Est. Priority Date: 04/30/2003
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Negley, Gerald H.
• Primary Examiner(s): Wilson; Allan R.
• Application Number:
  US10/818,592
• Publication Number:
  US 20040217360A1
• Time in Patent Office: 2,226 Days
• Field of Search: 257/99, 257/E33.062, 257/E33.066
• US Class Current: 257/99
• CPC Class Codes: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body

Abstract

A light-emitting device includes a substrate having first and second opposing surfaces. An active region is on the first surface and first and second electrical contacts are adjacent to the second surface and are conductively coupled to the active region. In other embodiments, a light-emitting device includes a substrate having first and second opposing surfaces. An active region is on the first surface and includes a first active layer having a first conductivity type on the first surface and a second active layer having a second conductivity type on the first active layer. A first electrical contact is adjacent to the second surface. A contact plug extends through the substrate and the active region and couples the first electrical contact to the second active layer. A second electrical contact is coupled to the substrate at the second surface.

Claims

1. A light-emitting device, comprising:

first and second opposing surfaces of a layer;

an active region comprising a first active layer having a first conductivity type on the first surface and a second active layer having a second conductivity type on the first active layer;

a first electrical contact adjacent to the second surface;

a partially transparent current spreading layer on the second active layer;

a contact plug that is substantially non-adjacent an edge of the active region and extending through the active region to contact the current spreading layer so as to couple the first electrical contact to the second active layer; and

a second electrical contact that is coupled to the second surface without extending through the second surface,

wherein the current spreading layer forms an ohmic contact with the second active layer, and

wherein the ohmic contact comprises a reflective ohmic contact.

2. The light-emitting device of claim 1, further comprising

a dielectric spacer on sides of the contact plug that separate the contact plug from the first active layer and in contact with the current spreading layer,

wherein the dielectric spacer comprises spin-on-glass and/or a polyimide.

3. The light-emitting device of claim 1, wherein the ohmic contact layer comprises at least one of TiN, platinum, nickel/gold, nickel oxide/gold, nickel oxide/platinum, Ti, and titanium/gold.

4. The light-emitting device of claim 3, wherein the ohmic contact layer has a thickness between about 10 Å

and about 100 Å

.

5. The light-emitting device of claim 1, further comprising:

a buffer layer adjacent the active region, the contact plug extending through the buffer layer.

6. The light-emitting device of claim 5, wherein the buffer layer comprises aluminum nitride.

7. The light-emitting device of claim 1, further comprising a substrate comprising the first and second opposing surfaces, wherein the substrate comprises SiC.

8. The light-emitting device of claim 1, wherein the contact plug comprises gold, silver, a gold alloy, and/or a silver alloy.

9. The light-emitting device of claim 1, wherein the first conductivity type is n-type, and wherein the second electrical contact comprises at least one of aluminum and titanium.

10. The light-emitting device of claim 1, wherein the second conductivity type is p-type, and wherein the first electrical contact comprises at least one of platinum, nickel, and titanium/gold.

11. The light-emitting device of claim 1, wherein the first active layer comprises GaN.

12. The light-emitting device of claim 1, wherein the second active layer comprises GaN.

13. A light-emitting device, comprising:

first and second opposing surfaces of a layer;

an active region on the first surface, the active region including a first active layer having a first conductivity type on the first surface and a second active layer having a second conductivity type on the first active layer;

a partially transparent current spreading layer on the second active layer of the active region, the current spreading layer including a reflective ohmic contact that is substantially non-adjacent an edge of the active region; and

first and second electrical contacts adjacent to the second surface that are conductively coupled to the active region, at least one of the first and second electrical contacts being disposed on the second surface without extending through the substrate.

14. The light-emitting device of claim 13, further comprising

a contact plug extending through the active region to contact the current spreading layer so as to couple the first electrical contact to the second active layer.

15. The light-emitting device of claim 14, further comprising:

a dielectric spacer on sides of the contact plug that separate the contact plug from the first active layer.

16. The light-emitting device of claim 15, wherein the dielectric spacer comprises spin-on-glass and/or a polyimide.

17. The light-emitting device of claim 13, wherein the reflective ohmic contact layer comprises at least one of nickel oxide/gold and nickel oxide/platinum.

18. The light-emitting device of claim 17, wherein the reflective ohmic contact layer has a thickness between about 10 Å

and about 100 Å

.

19. The light-emitting device of claim 14, further comprising:

a buffer layer between the active region and the first surface, the contact plug extending through the buffer layer.

20. The light-emitting device of claim 19, wherein the buffer layer comprises aluminum nitride.

21. The light-emitting device of claim 14, wherein the contact plug comprises gold, silver, a gold alloy, and/or a silver alloy.

22. The light-emitting device of claim 13, wherein the first conductivity type is n-type, and wherein the second electrical contact comprises at least one of aluminum and titanium.

23. The light-emitting device of claim 13, wherein the second conductivity type is p-type, and wherein the first electrical contact comprises at least one of platinum, nickel, and titanium/gold.

24. The light-emitting device of claim 13, wherein the first active layer comprises GaN.

25. The light-emitting device of claim 13, wherein the second active layer comprises GaN.

26. The light-emitting device of claim 13, further comprising a substrate comprising the first and second opposing surfaces, wherein the substrate comprises SiC.

27. A method of forming a light-emitting device, comprising:

forming an active region on a first surface of first and second opposing surfaces of a layer;

forming a partially transparent current spreading layer on the active region, the current spreading layer including a reflective ohmic contact with the active region, wherein the reflective ohmic contact is substantially non-adjacent an edge of the active region;

forming first and second electrical contacts adjacent to the second surface that are conductively coupled to the active region such that at least one of the first and second electrical contacts is disposed on the second surface without extending through the active region.

28. The method of claim 27, wherein forming the active region comprises:

forming a first active layer having a first conductivity type on the first surface and;

forming a second active layer having a second conductivity type on the first active Layer; and

wherein forming the current spreading layer comprises forming the current spreading layer on the second active layer.

29. The method of claim 28, further comprising:

forming a contact plug extending through the active region to contact the current spreading layer so as to couple the first electrical contact to the second active layer.

30. The method of claim 29, further comprising:

forming a dielectric spacer on sides of the contact plug that separate the contact plug from the first active layer.

31. The method of claim 29, further comprising:

forming a buffer layer between the active region and a substrate that includes the first and second opposing surfaces, the contact plug extending through the buffer layer.

32. A light-emitting device, comprising:

a flat planar surface defining a planar surface area and comprising first and second contact surfaces;

an active region on the flat planar surface, the active region including a first active layer having a first conductivity type and a second active layer on the first active layer having a second conductivity type;

a current spreading layer on the second active layer of the active region;

a contact plug that is substantially non-adjacent an edge of the active region and that extends through the active region to contact the current spreading layer, the contact plug comprising the first contact surface;

a first electrical contact that is within the planar surface area, the first electrical contact on the first contact surface and adjacent the second contact surface, the first electrical contact conductively coupled to the second active layer through the current spreading layer via the contact plug; and

a second electrical contact that is within the planar surface area, the second electrical contact on the second contact surface and conductively coupled to the first active layer.

33. A device according to claim 32, wherein the current spreading layer is at least partially transparent.

34. A device according to claim 33, wherein the current spreading layer comprises a reflective ohmic contact with the second active layer.

35. A device according to claim 32, wherein the reflective ohmic contact comprises at least one of nickel oxide/gold and nickel oxide/platinum.

36. A device according to claim 32, further comprising a dielectric spacer on sides of the contact plug that separate the contact plug from the first active layer.

37. A device according to claim 36, wherein the dielectric spacer comprises spin-on-glass and/or a polyimide.