HIGH EFFICIENCY LEDS AND METHODS OF MANUFACTURING

• US 20160211420A1
• Filed: 01/21/2015
• Published: 07/21/2016
• Est. Priority Date: 01/21/2015
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: KAR, PRITISH, GOLAKIA, HARSHAD, ACHARYA, RAJEEV, DORA, YUVARAJ, DONOFRIO, MATTHEW, HEIKMAN, STEN
• Granted Patent: US 10,658,546 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 2933/0025 relating to coatings
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• 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 33/38 with a particular shape
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Simplified LED chip architectures or chip builds are disclosed that can result in simpler manufacturing processes using fewer steps. The LED structure can have fewer layers than conventional LED chips with the layers arranged in different ways for efficient fabrication and operation. The LED chips can comprise an active LED structure. A dielectric reflective layer is included adjacent to one of the oppositely doped layers. A metal reflective layer is on the dielectric reflective layer, wherein the dielectric and metal reflective layers extend beyond the edge of said active region. By extending the dielectric layer, the LED chips can emit with more efficiency by reflecting more LED light to emit in the desired direction. By extending the metal reflective layer beyond the edge of the active region, the metal reflective layer can serve as a current spreading layer and barrier, in addition to reflecting LED light to emit in the desired direction. The LED chips can also comprise self-aligned and self-limiting features that simplify etching processes during fabrication.

Claims

1. A light emitting diode (LED) chip, comprising:

an active LED structure comprising an active region between two oppositely doped layers, and said active region emitting light in response to an electrical signal applied to said oppositely doped layer;

a first reflective layer adjacent one of said oppositely doped layers;

a second reflective layer on said first reflective layer, said second reflective layer reflecting light not reflected by said first reflective layer, wherein at least one of said first and said second reflective layers extend beyond the edge of said active LED structure.

2. The LED chip of claim 1, wherein the first reflective layer extends beyond the edge of said active LED structure.

3. The LED chips of claim 1, wherein said second reflective layer extends beyond the edge of said active LED structure.

4. The LED chip of claim 1, wherein both the first and second reflective layers extend beyond the edge of said active LED structure.

5. The LED chip of claim 1, wherein said first reflective layer comprises a dielectric material.

6. The LED chip of claim 1, wherein said first reflective layer comprises SiO₂, SiN, Si, Ge, MgOx, MgNx, ZnO, SiNx, SiOx, AlN and alloys or combinations thereof.

7. The LED chip of claim 1, wherein said second reflective layer comprises a metal.

8. The LED chip of claim 1, wherein said second reflective layer comprises a metal stack.

9. The LED chip of claim 1, further comprising a current spreading layer between said first reflective layer and said active LED structure.

10. The LED chip of claim 1, further comprising a p-contact, wherein said p-contact is on said second reflective layer.

11. The LED chip of claim 7, wherein said p-contact is arranged in a hole through said first reflective layer.

12. The LED chip of claim 1, wherein said first reflective layer extends beyond the edge of one or more layers of said active structure.

13. The LED chip of claim 1, wherein said first reflective layer terminates before the edge of said LED chip.

14. The LED chip of claim 1, wherein said first reflective layer terminates at the edge of said LED chip.

15. The LED chip of claim 1, wherein said first reflective layer terminates between the edge of said active region and the edge of said n-type layer.

16. The LED chip of claim 1, wherein said first and/or second reflective layers form a reflective cup.

17. The LED chip of claim 1, wherein said reflective cup comprises an upward extending portion that reflects emitted laterally in said active structure.

18. The LED chip of claim 1, comprising a self-aligned via hole through said first and second reflectors to said active structure.

19. The LED chip of claim 1, further comprising textured features on said active structure.

20. The LED chip of claim 19, wherein said textured features are self-limiting to an etch.

21. A light emitting diode (LED) chip, comprising:

an active LED structure comprising an active region between two oppositely doped layers, and said active region emitting light in response to an electrical signal applied to said oppositely doped layer;

a dielectric reflective layer on one of said oppositely doped layers and extending beyond the edge of said active region;

a metal reflective layer on said first dielectric reflective layer.

22. The LED chip of claim 21, wherein said dielectric reflective layer extends beyond the edge of said n-type layer.

23. The LED chip of claim 21, wherein said dielectric reflective layer terminates before the edge of said LED chip.

24. The LED chip of claim 21, wherein said dielectric reflective layer terminates at the edge of said LED chip.

25. The LED chip of claim 21, wherein said dielectric reflective layer terminates between the edge of said active region and the edge of said n-type layer.

26. The LED chip of claim 21, wherein said dielectric reflective and/or said metal layer form a reflective cup.

27. The LED chip of claim 21, wherein said metal reflective layer extends beyond the edge of said active structure.

28. The LED chip of claim 27, further comprising a p-contact, wherein said p-contact is on said metal reflective layer.

29. The LED chip of claim 27, wherein said p-contact passes through said dielectric layer and is directly on said metal reflective layer.

30. The LED chip of claim 21, comprising a self-aligned via hole through said dielectric and metal reflective layer to said active structure.

31. The LED chip of claim 21, further comprising self-limiting textured features on said active structure.

32. A method for forming LED chips, comprising:

depositing active structure epitaxial layers on a wafer;

etching different portions of said active structure in a single etch step, wherein said different portions etch at different rates and wherein at least one of said portions is self-limiting to said etch.

33. The method of claim 33, wherein said self-limiting portions comprise textured features on said active structure.

34. The method of claim 33, further comprising forming an array of mask features on said active structure, said etch etching the active structure between said mask features.

35. The method of claim 33, wherein another of said at least one of said portions comprises streets formed between active structure mesas.

36. The method of claim 33, further comprising forming a plurality of reflective layers on said active epitaxial layers.

38. The method of claim 33, further comprising forming a plurality of reflective layers on said active epitaxial layers, with one or more of said reflective layers extending beyond the edge of said active structure mesas.

37. The method of claim 37, further comprising a single etch step to form a self-aligned via hole through said reflective layers to said active structure.

39. The method of claim 39, further comprising forming a contact on one of said reflective layers.

40. The method of claim 39, wherein one or more of said plurality of refelective layers forms a reflective cup.

41. A method for forming LED chips, comprising:

forming an active structure of epitaxial layers;

forming a plurality of reflective layers on said active structure;

performing a single etch step to form a self-aligned via hole through said reflective layers to said active structure.

42. A light emitting diode (LED) chip, comprising:

an active LED structure;

a first reflective layer adjacent said active layer;

a second reflective layer on said first reflective layer, said second reflective layer reflecting light not reflected by said first reflective layer, wherein said first reflective layer extends beyond the active region on a portion of the LED chip.

43. The LED chip of claim 42, wherein said first reflective layer extends beyond the active region on substantially all of the LED chip.

44. The LED chip of claim 42, wherein said second reflective layer extends beyond said active region on a portion of the LED chip.

45. The LED chip of claim 42, wherein said second reflective layer extends beyond said active region on substantially all of the LED chip.

46. The LED chip of claim 45, further comprising a contact on said second reflector.

47. The LED chip of claim 45, wherein said contact passes through said first reflective layer.

48. A light emitting diode (LED) chip, comprising:

an active LED structure;

a plurality of layers on the backside of said active structure;

a via hole on the backside of and into said active LED structure, wherein at least two of said plurality of layers are self-aligned at said via hole.

49. The LED chip of claim 48, wherein said plurarity of layers comprises a current spreading layer and a first reflective layer self-aligned at said via hole.

50. The LED chip of claim 48, wherein said first reflective layer comprises a dielectric material.

51. The LED chip of claim 48, wherein said plurality of active layers further comprises a second reflective layer self-aligned at said vias hole.

52. The LED chip of claim 51, wherein said second reflective layer comprises a metal.

53. A light emitting diode (LED) chip, comprising:

an active LED structure;

a plurality of layers on the backside of said active structure;

wherein one or more of said plurality of layers self-aligned at more than one location on the backside of said active structure.

54. The LED chip of claim 53, further comprising a via hole, wherein one of said plurality of layers comprises a first layer self-aligned at said via hole and at the edge of said active structure.

55. The LED chip of claim 54, wherein said first layer comprises a current spreading layer.

56. The LED chip of claim 54, wherein said plurality of layers further comprises a second layer on said first layer, wherein said second layer is self-aligned at said via hole and/or at the edge of said active structure.

57. The LED chip of claim 56, wherein said second layer comprises a dielectric reflective layer.

58. The LED chip of claim 56, wherein said plurality of layers further comprises a third layer on said second layer, where said third layer is self-aligned at said via hole and/or the edge of said active structure.

59. The LED chip of claim 58, wherein said third layer comprises a metal reflective layer.