High efficiency LEDs and methods of manufacturing

• US 10,658,546 B2
• Filed: 01/21/2015
• Issued: 05/19/2020
• Est. Priority Date: 01/21/2015
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew, Kar, Pritish, Heikman, Sten, Golakia, Harshad, Acharya, Rajeev, Dora, Yuvaraj
• Primary Examiner(s): Hoang, Tuan A
• Application Number:
  US14/602,040
• Publication Number:
  US 20160211420A1
• Time in Patent Office: 1,945 Days
• Field of Search: 257 40, 257 98, 257 99, 257 91, 257E33068, 438 29
• 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, said active region emitting light in response to an electrical signal applied to at least one of said oppositely doped layers;

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

a second reflective layer, said first reflective layer between said active region and said second reflective layer said second reflective layer reflecting light not reflected by said first reflective layer, wherein said second reflective layer extends beyond an outer edge of said active LED structure and into a street, said street outside of said active region, wherein said first and second reflective layers are spaced away from said active LED structure such that neither of said first and second reflective layers directly contacts said active LED structure; and

a contact in said street and on a portion of said second reflective layer that extends beyond said outer edge of said active LED structure and into said street, wherein said contact extends through said first reflective layer and contacts a top of said portion of said second reflective layer.

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

3. The LED chip of claim 2, wherein said contact extends to said portion of said second reflective layer by extending through a portion of said first reflective layer that extends beyond said outer edge of said active LED structure and into said street.

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

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

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

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

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

9. The LED chip of claim 1, wherein said contact is a p-contact.

10. The LED chip of claim 9, wherein said p-contact is in a hole through said first reflective layer.

11. The LED chip of claim 1, wherein said contact is in a hole through said first reflective layer.

12. The LED chip of claim 1, wherein said first reflective layer terminates before an end of said LED chip.

13. The LED chip of claim 1, wherein said first reflective layer terminates at an end of said LED chip.

14. The LED chip of claim 1, said active LED structure comprising an n-type layer and a p-type layer, wherein said first reflective layer terminates between an edge of said p-type layer and an edge of said n-type layer.

15. The LED chip of claim 1, wherein said first reflective layer forms a reflective cup.

16. The LED chip of claim 15, wherein said reflective cup comprises an upward extending portion that reflects light emitted laterally in said active LED structure.

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

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

19. The LED chip of claim 18, wherein said textured features are self-limiting to an etch.

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

an active LED structure comprising an active region between two oppositely doped layers, said active region emitting light in response to an electrical signal applied to at least one of said oppositely doped layers, said active LED structure comprising an n-type layer;

a current spreading layer on said active LED structure;

a dielectric reflective layer on said current spreading layer;

a metal reflective layer on said dielectric reflective layer, said dielectric reflective layer between said current spreading layer and said metal reflective layer; and

wherein said dielectric reflective layer and said metal reflective layer are separated from said active LED structure;

wherein said current spreading layer, said dielectric reflective layer, and said metal reflective layer extend beyond an outer edge of said active region and into a street, said street outside of said active region; and

a contact in said street, said contact extending through said current spreading layer and said dielectric reflective layer to said metal reflective layer so as to contact said metal reflective layer.

21. The LED chip of claim 20, wherein said dielectric reflective layer extends beyond an edge of said n-type layer.

22. The LED chip of claim 20, wherein said dielectric reflective layer terminates before an edge of said LED chip.

23. The LED chip of claim 20, wherein said dielectric reflective layer terminates at an edge of said LED chip.

24. The LED chip of claim 20, wherein said current spreading layer and said metal reflective layer are connected by one or more metal vias.

25. The LED chip of claim 20, wherein said contact extends through said current spreading layer and said dielectric reflective layer to a portion of said metal reflective layer that is in said street.

26. The LED chip of claim 25, wherein said contact is a p-contact.

27. The LED chip of claim 20, wherein said contact extends through a portion of said current spreading layer in said street and a portion of said dielectric reflective layer in said street to a portion of said metal reflective layer in said street.

28. The LED chip of claim 20, comprising a self-aligned via hole through said dielectric and metal reflective layers to said active LED structure.

29. The LED chip of claim 20, further comprising self-limiting textured features on said active LED structure.

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

an active region;

a first reflective layer on said active region; and

a second reflective layer on said first reflective layer such that said first reflective layer is between said active region and said second reflective layer, said second reflective layer reflecting light not reflected by said first reflective layer, wherein said first reflective layer and said second reflective layer extend beyond an outer edge of the active region on a portion of the LED chip and into a street, said street outside of said active region, wherein said second reflective layer is a metal reflective layer; and

a contact in said street and extending through said first reflective layer to contact said second reflective layer.

31. The LED chip of claim 30, wherein said second reflective layer extends beyond said active region on substantially all of the LED chip.

32. The LED chip of claim 30, further comprising a contact on a portion of said second reflective layer that is in said street.

33. The LED chip of claim 32, wherein said contact passes through a portion of said first reflective layer that is in said street.

34. The LED chip of claim 30, wherein said first reflective layer overlaps all of said active region in a vertical direction.

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

an active LED structure comprising an active region;

a plurality of layers on a backside of said active LED structure, said plurality of layers comprising a first reflective layer and a second reflective layer, said first reflective layer and said second reflective layer extending into a street, said street outside of said active region;

a contact in said street, through a portion of first reflective layer that is in said street, and contacting a portion of said second reflective layer that is in said street; and

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;

wherein said first and second reflective layers are spaced away from said active LED structure such that neither of said first and second reflective layers directly contacts said active LED structure.

36. The LED chip of claim 35, wherein said plurality of layers further comprises a current spreading layer, said current spreading layer and said first reflective layer self-aligned at said via hole.

37. The LED chip of claim 36, wherein said first reflective layer comprises a dielectric material.

38. The LED chip of claim 35, wherein said second reflective layer is self-aligned at said via hole.

39. The LED chip of claim 37, wherein said second reflective layer comprises a metal.

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

an active LED structure comprising an active region;

a plurality of layers on a backside of said active LED structure, said plurality of layers comprising a dielectric reflective layer and a metal reflective layer, said dielectric reflective layer extending into a street, said street outside of said active region; and

wherein two or more of said plurality of layers are self-aligned in said street and on said backside of said active LED structure, wherein the self-alignment forms a hole through said first reflective layer, and further comprising a contact in said hole and contacting said second reflective layer; and

wherein said dielectric reflective layer and said metal reflective layer are separated from said active LED structure.

41. The LED chip of claim 40, further comprising a via hole, wherein a first of said plurality of layers is self-aligned at said via hole and at an edge of said active LED structure.

42. The LED chip of claim 41, wherein said plurality of layers further comprises a current spreading layer, and wherein said first of said plurality of layers is said current spreading layer.

43. The LED chip of claim 41, wherein a second of said plurality of layers is self-aligned at said via hole and at said edge of said active LED structure.

44. The LED chip of claim 43, wherein said second of said plurality of layers is said dielectric reflective layer.

45. The LED chip of claim 43, wherein a third of said plurality of layers is self-aligned at said via hole and at said edge of said active LED structure.

46. The LED chip of claim 45, wherein said third of said plurality of layers is said metal reflective layer.

47. The LED chip of claim 40, wherein said two or more of said plurality of layers are vertically self-aligned.

48. The LED chip of claim 40, wherein said two or more of said plurality of layers are self-aligned at more than one location.