Light emitting devices having current reducing structures and methods of forming light emitting devices having current reducing structures

• US 20080217635A1
• Filed: 03/08/2007
• Published: 09/11/2008
• Est. Priority Date: 06/30/2004
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew, Bergmann, Michael John, Emerson, David Todd, Edmond, John, Haberern, Kevin, Slater, David B.
• Granted Patent: US 7,795,623 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/145 with a current-blocking structure
• CPC Class Codes: H01L 33/38 with a particular shape

Abstract

A light emitting device includes a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer. A non-transparent feature, such as a wire bond pad, is on the p-type semiconductor layer or on the n-type semiconductor layer opposite the p-type semiconductor layer, and a reduced conductivity region is in the p-type semiconductor layer or the n-type semiconductor layer and is aligned with the non-transparent feature. The reduced conductivity region may extend from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region and/or from a surface of the n-type semiconductor layer opposite the p-type semiconductor layer towards the active region.

Claims

1. A light emitting device, comprising:

a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer;

a non-transparent feature on the p-type semiconductor layer or on the n-type semiconductor layer opposite the p-type semiconductor layer; and

a reduced conductivity region in the p-type semiconductor layer and aligned with the non-transparent feature, the reduced conductivity region extending from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region.

2. The light emitting device of claim 1, wherein the non-transparent region comprises a bond pad, a passivation region, and/or a current spreading finger.

3. The light emitting device of claim 1, further comprising a substrate including first and second opposing surfaces, wherein the n-type semiconductor is on the first surface of the substrate and wherein the non-transparent feature is on the second surface of the substrate opposite the n-type semiconductor layer.

4. The light emitting device of claim 1, further comprising a metal stack on the surface of the p-type semiconductor layer.

5. The light emitting device of claim 4, wherein the metal stack comprises an ohmic layer directly on the p-type semiconductor layer, and a reflective layer on the ohmic layer.

6. The light emitting device of claim 5, wherein the metal stack comprises a bonding layer on the reflective layer.

7. The light emitting device of claim 5, further comprising a barrier layer between the reflective layer and the bonding layer.

8. The light emitting device of claim 1, wherein the reduced conductivity region extends from the surface of the p-type semiconductor layer to the active region.

9. The light emitting device of claim 1, wherein the reduced conductivity region extends from the surface of the p-type semiconductor layer into the active region.

10. The light emitting device of claim 1, wherein the reduced conductivity region extends from the surface of the p-type semiconductor layer through the active region.

11. The light emitting device of claim 1, wherein the reduced conductivity region extends through the p-type semiconductor layer, the active region and into the n-type semiconductor layer.

12. The light emitting device of claim 11, wherein the non-transparent feature comprises a wire bond pad in contact with the reduced conductivity region, the light emitting device further comprising an ohmic contact on the n-type semiconductor layer adjacent and in electrical contact with the wire bond pad.

13. The light emitting device of claim 1, wherein the reduced conductivity region extends completely through the n-type semiconductor layer.

14. The light emitting device of claim 1, wherein the active region comprises a Group III-nitride based active region.

15. The light emitting device of claim 1, wherein the reduced conductivity region comprises an insulating region.

16. The light emitting device of claim 1, wherein the reduced conductivity region comprises a region that is not non-transparent.

17. The light emitting device of claim 1, wherein the reduced conductivity region comprises an implanted region.

18. The light emitting device of claim 4, wherein the reduced conductivity region corresponds to a region of damage at an interface between the metal stack and the p-type semiconductor layer.

19. The light emitting device of claim 18, wherein the region of damage comprises a wet or dry etched region of the p-type semiconductor layer.

20. The light emitting device of claim 18, wherein the region of damage comprises a region of the p-type semiconductor layer exposed to a high energy plasma.

21. The light emitting device of claim 18, wherein the region of damage comprises a region of the p-type semiconductor layer exposed to H₂.

22. The light emitting device of claim 18, wherein the region of damage comprises a region of the p-type semiconductor layer exposed to a high energy laser.

23. A light emitting device, comprising:

a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer;

a non-transparent feature on the n-type semiconductor layer opposite the p-type semiconductor layer; and

a metal contact on a surface of the p-type semiconductor layer opposite the n-type semiconductor layer, wherein the metal contact forms on ohmic contact to the p-type semiconductor layer in a region other than a reduced conductivity area of the surface of the p-type semiconductor layer that is aligned with the non-transparent feature.

24. The light emitting device of claim 23, wherein the non-transparent region comprises a bond pad, a passivation region, and/or a current spreading finger.

25. The light emitting device of claim 23, further comprising a reduced conductivity region in the p-type semiconductor layer and aligned with the non-transparent feature and the reduced conductivity area, the reduced conductivity region extending from the surface of the p-type semiconductor layer towards the active region.

26. The light emitting device of claim 23, further comprising a reduced conductivity region in the n-type semiconductor layer and aligned with the non-transparent feature, the reduced conductivity region extending from a surface of the n-type semiconductor layer opposite the p-type semiconductor layer towards the active region.

27. The light emitting device of claim 23, further comprising a non-ohmic contact on the surface of the p-type semiconductor layer.

28. The light emitting device of claim 27, wherein the non-ohmic contact comprises a metal that does not form an ohmic contact with the p-type semiconductor layer.

29. The light emitting device of claim 27, wherein the non-ohmic contact comprises an insulator on the surface of the p-type semiconductor layer.

30. A light emitting device, comprising:

a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer;

a wire bond pad on the n-type semiconductor layer opposite the p-type semiconductor layer;

a reduced conductivity region in the n-type semiconductor layer and aligned with the wire bond pad, the reduced conductivity region extending from a surface of the n-type semiconductor layer opposite the p-type semiconductor layer towards the active region; and

an ohmic contact on the n-type semiconductor layer adjacent and in electrical contact with the wire bond pad.

31. The light emitting device of claim 30, further comprising a metal stack on a surface of the p-type semiconductor layer opposite the n-type semiconductor layer.

32. The light emitting device of claim 31, wherein the metal stack comprises an ohmic layer directly on the p-type semiconductor layer, and a reflective layer on the ohmic layer.

33. The light emitting device of claim 32, wherein the metal stack comprises a bonding layer on the reflective layer.

34. The light emitting device of claim 30, wherein the reduced conductivity region comprises a first reduced conductivity region, the light emitting device further comprising a second reduced conductivity region in the p-type semiconductor layer and aligned with the wire bond pad, the second reduced conductivity region extending from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region.

35. The light emitting device of claim 30, further comprising a metal contact on a surface of the p-type semiconductor layer opposite the n-type semiconductor layer, wherein the metal contact forms on ohmic contact to the p-type semiconductor layer in a region other than a reduced conductivity area of the surface of the p-type semiconductor layer that is aligned with the wire bond pad.

36. The light emitting device of claim 30, further comprising a non-ohmic contact on the reduced conductivity area of the surface of the p-type semiconductor layer.

37. The light emitting device of claim 36, wherein the non-ohmic contact comprises a metal that does not form an ohmic contact with the p-type semiconductor layer.

38. The light emitting device of claim 36, wherein the non-ohmic contact comprises an insulator on the surface of the p-type semiconductor layer.

39. The light emitting device of claim 30, wherein the reduced conductivity region corresponds to a region of damage at an interface between the n-type semiconductor layer and the wire bond pad.

40. The light emitting device of claim 39, wherein the region of damage comprises a wet or dry etched region of the n-type semiconductor layer.

41. The light emitting device of claim 39, wherein the region of damage comprises a region of the n-type semiconductor layer exposed to a high energy plasma.

42. The light emitting device of claim 39, wherein the region of damage comprises a region of the n-type semiconductor layer exposed to H₂.

43. The light emitting device of claim 39, wherein the region of damage comprises a region of the n-type semiconductor layer exposed to a high energy laser.

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

forming a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer;

forming a non-transparent feature on the n-type semiconductor layer opposite the p-type semiconductor layer; and

forming a reduced conductivity region in the p-type semiconductor layer and aligned with the non-transparent feature, the reduced conductivity region extending from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region.

45. The method of claim 44, wherein forming a non-transparent feature on the n-type semiconductor layer comprises forming a wire bond pad, a current spreading finger and/or a passivation region on the n-type semiconductor layer.

46. The method of claim 44, wherein the reduced conductivity region extends from the surface of the p-type semiconductor layer to the active region.

47. The method of claim 44, wherein the reduced conductivity region extends from the surface of the p-type semiconductor layer into the active region.

48. The method of claim 44, wherein the reduced conductivity region extends from the surface of the p-type semiconductor layer through the active region.

49. The method of claim 44, wherein the reduced conductivity region extends through the active region.

50. The method of claim 44, wherein the active region comprises a Group III-nitride based active region.

51. The method of claim 44, wherein forming a reduced conductivity region comprises:

forming a mask layer on the surface of the p-type semiconductor layer, the mask layer having an opening corresponding to the bond pad region; and

implanting atoms into the p-type semiconductor layer through the opening in the mask layer.

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

forming a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer;

forming a wire bond pad on the n-type semiconductor layer opposite the p-type semiconductor layer; and

forming a metal contact on a surface of the p-type semiconductor layer opposite the n-type semiconductor layer, wherein the metal contact forms on ohmic contact to the p-type semiconductor layer in a region other than a reduced conductivity area of the surface of the p-type semiconductor layer that is aligned with the wire bond pad.

53. The method of claim 52, further comprising forming a reduced conductivity region in the p-type semiconductor layer and aligned with the wire bond pad and the reduced conductivity area, the reduced conductivity region extending from the surface of the p-type semiconductor layer towards the active region.

54. The method of claim 52, further comprising forming a reduced conductivity region in the n-type semiconductor layer and aligned with the wire bond pad, the reduced conductivity region extending from a surface of the n-type semiconductor layer opposite the p-type semiconductor layer towards the active region.

55. The method of claim 52, further comprising forming a non-ohmic contact on the surface of the p-type semiconductor layer.

56. The method of claim 55, wherein the non-ohmic contact comprises a metal that does not form an ohmic contact with the p-type semiconductor layer.

57. The method of claim 55, wherein the non-ohmic contact comprises an insulator on the surface of the p-type semiconductor layer.

58. A light emitting device, comprising:

a p-type semiconductor layer, an n-type semiconductor layer, and an active region between the n-type semiconductor layer and the p-type semiconductor layer;

a bond pad on the p-type semiconductor layer opposite the n-type semiconductor layer; and

a reduced conductivity region in the p-type semiconductor layer and aligned with the bond pad, the reduced conductivity region extending from a surface of the p-type semiconductor layer opposite the n-type semiconductor layer towards the active region.

59. The light emitting device of claim 58, further comprising a reflector between the bondpad and the p-type semiconductor layer.

60. The light emitting device of claim 58, further comprising a current spreading finger on the p-type semiconductor layer, wherein the reduced conductivity region is further aligned with the current spreading finger.