Solid state light emitting device and method of making same

• US 8,008,676 B2
• Filed: 05/24/2007
• Issued: 08/30/2011
• Est. Priority Date: 05/26/2006
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Hunter, F. Neal, Negley, Gerald H.
• Primary Examiner(s): TRAN, MINH LOAN
• Application Number:
  US11/753,103
• Publication Number:
  US 20070280624A1
• Time in Patent Office: 1,559 Days
• Field of Search: 257/98, 257/99, 257/100, 257/103, 257/E33.067, 257/E33.072
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

There is provided a solid state light emitting device comprising at least one light emitting active layer structure and at least one structure selected from among: (1) a first element having at least a first region which has an index of refraction gradient, (2) a first element, at least a portion of which has an index of refraction which is lower than an index of refraction of a side of the active layer, (3) first and second elements, in which one side of the second element is positioned on a side of the active layer and the first element is positioned on the other side of the second element, and in which at least a portion of the first element has an index of refraction which is lower than the index of refraction of at least a portion of the second element. Also provided are methods of making such devices.

Claims

1. A solid state light emitting device comprising:

a first element, at least a first region of said first element having an index of refraction gradient;

at least one light emitting active layer structure, said first element on said light emitting active layer structure; and

at least one second structure selected from (1) at least one lumiphor and (2) at least one encapsulant region, said first element between said second structure and said light emitting active layer structure, so that at least some light emitted from the light emitting active layer passes through the first element and then through the second structure,

a first surface of said light emitting active layer structure facing said first element and in direct contact with said first element, a first region of said light emitting active layer structure comprising at least a portion of said first surface of said light emitting active layer structure, said first region of said light emitting active layer structure having an active layer first region index of refraction,

a second surface of said second structure facing said first element, a second region of said second structure comprising at least a portion of said second surface of said second structure, said second region of said second structure having a second structure second region index of refraction,

said index of refraction gradient ranging from said active layer first region index of refraction to said second structure second region index of refraction.

2. A device as recited in claim 1, further comprising at least a first intervening structure between said first element and said light emitting active layer structure.

3. A device as recited in claim 2, wherein said first intervening structure has an index of refraction which is similar to an index of refraction of at least a portion of said first element.

4. A device as recited in claim 2, wherein said first intervening structure has an index of refraction which is similar to an index of refraction of at least a portion of said light emitting active layer structure.

5. A device as recited in claim 2, wherein said first intervening structure comprises glue.

6. A device as recited in claim 1, wherein said index of refraction gradient of said first element comprises a stepped index of refraction gradient.

7. A device as recited in claim 1, wherein said index of refraction gradient of said first element comprises a substantially continuous index of refraction gradient.

8. A device as recited in claim 1, wherein a surface of said first element which is opposite to said light emitting active layer structure comprises at least one optical feature.

9. A device as recited in claim 1, wherein said lumiphor is on said first element.

10. A device as recited in claim 9, wherein said lumiphor is in direct contact with said first element.

11. A device as recited in claim 1, wherein said lumiphor is spaced from said first element, at least a portion of a space between said lumiphor and said first element comprising a gas.

12. A device as recited in claim 11, wherein said gas comprises air.

13. A device as recited in claim 1, wherein said encapsulant region is on said first element.

14. A device as recited in claim 13, wherein said encapsulant region is in direct contact with said first element.

15. A device as recited in claim 13, further comprising at least one lumiphor, at least a portion of said lumiphor between said first element and said encapsulant region, whereby if light is emitted from said light emitting active layer structure and passes through said first element, said lumiphor and said encapsulant region, such light would pass through said first element before passing through said lumiphor and would pass through said lumiphor before passing through said encapsulant region.

16. A device as recited in claim 15, wherein said lumiphor is on said first element.

17. A device as recited in claim 16, wherein said lumiphor is in direct contact with said first element.

18. A device as recited in claim 15, wherein said lumiphor is spaced from said first element, at least a portion of a space between said lumiphor and said first element comprising a gas.

19. A device as recited in claim 18, wherein said gas comprises air.

20. A device as recited in claim 1, wherein said encapsulant region is spaced from said first element, at least a portion of a space between said encapsulant region and said first element comprising a gas.

21. A device as recited in claim 20, wherein said gas comprises air.

22. A device as recited in claim 1, further comprising a second element, said light emitting active layer structure having an active layer structure first side and an active layer structure second side, said first element on said active layer first side, said active layer second side on said second element.

23. A device as recited in claim 22, wherein said light emitting active layer structure is in direct contact with said second element and said first element is in direct contact with said light emitting active layer structure.

24. A device as recited in claim 22, further comprising at least one reflective element between said second element and said light emitting active layer structure.

25. A device as recited in claim 24, wherein said reflective element is in direct contact with said second element, said light emitting active layer structure is in direct contact with said reflective element, and said first element is in direct contact with said light emitting active layer structure.

26. A device as recited in claim 22, further comprising at least one reflective element, said second element having a second element first side and a second element second side, said light emitting active layer on said second element first side, said reflective element on said second element second side.

27. A device as recited in claim 26, further comprising at least one bevel reflective element, said bevel reflective element on a second element third side, said second element third side extending between said second element first side and said second element second side.

28. A device as recited in claim 26, wherein said second element second side is in direct contact with said reflective element, said light emitting active layer structure is in direct contact with said second element first side, and said first element is in direct contact with said light emitting active layer structure.

29. A device as recited in claim 1, further comprising a second element, wherein said second element is on said light emitting active layer structure, and said first element is on said second element.

30. A device as recited in claim 29, wherein said second element is in direct contact with said light emitting active layer structure, and said first element is in direct contact with said second element.

31. A solid state light emitting device as recited in claim 1, wherein the light emitting device further comprises at least a first reflective element, at least a portion of the light emitting active layer structure between the first reflective element and the first element.

32. A solid state light emitting device comprising:

at least one light emitting active layer structure, said light emitting active layer structure having an active layer structure first surface and an active layer structure second surface, a first region of said light emitting active layer structure which includes at least a portion of said active layer structure first surface having an active layer first region index of refraction;

a first element on said active layer structure first surface; and

at least one second structure selected from (1) at least one lumiphor and (2) at least one encapsulant region, said first element between said second structure and said light emitting active layer structure, so that at least some light emitted from the light emitting active layer passes through the first element and then through the second structure,

said first surface of said light emitting active layer structure facing said first element,

a second surface of said second structure facing said first element, a second region of said second structure comprising at least a portion of said second surface of said second structure, said second region of said second structure having a second structure second region index of refraction,

an entirety of said first element having a first element index of refraction that is of a single value between said active layer first region index of refraction and said second structure second region index of refraction.

33. A device as recited in claim 32, wherein a surface of said first element which is opposite to said light emitting active layer structure comprises at least one optical feature.

34. A device as recited in claim 32, wherein said lumiphor is on said first element.

35. A device as recited in claim 34, wherein said lumiphor is in direct contact with said first element.

36. A device as recited in claim 32, wherein said lumiphor is spaced from said first element, at least a portion of a space between said lumiphor and said first element comprising a gas.

37. A device as recited in claim 36, wherein said gas comprises air.

38. A device as recited in claim 32, wherein said first element index of refraction is a geometric mean of said active layer first region index of refraction and said second structure second region index of refraction.

39. A device as recited in claim 32, further comprising a second element, said first element on said active layer first surface, said active layer second surface on said second element.

40. A device as recited in claim 39, further comprising at least one reflective element positioned between said second element and said light emitting active layer structure.

41. A device as recited in claim 39, further comprising at least one reflective element, said second element having a second element first side and a second element second side, said light emitting active layer on said second element first side, said reflective element on said second element second side.

42. A device as recited in claim 41, further comprising at least one bevel reflective element, said bevel reflective element on a second element third side, said second element third side extending between said second element first side and said second element second side.

43. A device as recited in claim 42, wherein said second element second side is in direct contact with said reflective element, said light emitting active layer structure is in direct contact with said second element first side, and said first element is in direct contact with said light emitting active layer structure.

44. A device as recited in claim 32, further comprising a second element, wherein said second element is positioned on said light emitting active layer structure, and said first element is positioned on said second element.

45. A solid state light emitting device as recited in claim 32, wherein the light emitting device further comprises at least a first reflective element, at least a portion of the light emitting active layer structure between the first reflective element and the first element.

46. A solid state light emitting device comprising:

at least one light emitting active layer structure, said light emitting active layer structure having an active layer structure first surface and an active layer structure second surface;

a first element on said active layer structure first surface, at least a portion of said first element having a stepped index of refraction.

47. A device as recited in claim 46, wherein a surface of said first element which is opposite to said light emitting active layer structure comprises at least one optical feature.

48. A device as recited in claim 46, wherein said device further comprises at least one second structure selected from (1) at least one lumiphor and (2) at least one encapsulant region, said second structure opposite said first element relative to said light emitting active layer structure, so that at least some light emitted from the light emitting active layer passes through the first element and then through the second structure.

49. A device as recited in claim 48, wherein said encapsulant region is on said first element.

50. A device as recited in claim 49, wherein said encapsulant region is in direct contact with said first element.

51. A device as recited in claim 48, wherein said encapsulant region is spaced from said first element, at least a portion of a space between said encapsulant region and said first element comprising a gas.

52. A device as recited in claim 51, wherein said gas comprises air.

53. A device as recited in claim 48, wherein said lumiphor is positioned on said first element.

54. A device as recited in claim 53, wherein said lumiphor is in direct contact with said first element.

55. A device as recited in claim 48, wherein said lumiphor is spaced from said first element, at least a portion of a space between said lumiphor and said first element comprising a gas.

56. A device as recited in claim 55, wherein said gas comprises air.

57. A device as recited in claim 46, wherein said device further comprises a space opposite said first element relative to said light emitting active layer structure, so that at least some light emitted from the light emitting active layer passes through the first element and then through the space.

58. A device as recited in claim 46, wherein a first surface of said first element is exposed to an exterior of said solid state lighting device.

59. A device as recited in claim 58, wherein an entirety of said first surface of said first element is exposed to an exterior of said solid state lighting device.

60. A solid state light emitting device as recited in claim 46, wherein the light emitting device further comprises at least a first reflective element, at least a portion of the light emitting active layer structure between the first reflective element and the first element.

61. A solid state light emitting device comprising:

at least one light emitting active layer structure, said light emitting active layer structure having an active layer structure first surface and an active layer structure second surface, a first region of said light emitting active layer structure which includes at least a portion of said active layer structure first surface having an active layer first region index of refraction;

a first element having a first element first surface and a first element second surface, said first element second surface on said active layer structure first surface, said first element first surface exposed to an exterior of said solid state lighting device, at least a first region of said first element having an index of refraction gradient, said index of refraction gradient ranging from a lower value to an upper value, said upper value not greater than said active layer first region index of refraction, said lower value lower than said upper value, but greater than 1.0.

62. A device as recited in claim 61, wherein said first element first side comprises at least one optical feature.

63. A device as recited in claim 61, further comprising a second element, said first element on said active layer first surface, said active layer second surface on said second element.

64. A device as recited in claim 63, further comprising at least one reflective element between said second element and said light emitting active layer structure.

65. A device as recited in claim 63, further comprising at least one reflective element, said second element having a second element first side and a second element second side, said light emitting active layer on said second element first side, said reflective element on said second element second side.

66. A device as recited in claim 65, further comprising at least one bevel reflective element, said bevel reflective element on a second element third side, said second element third side extending between said second element first side and said second element second side.

67. A device as recited in claim 66, wherein said second element second side is in direct contact with said reflective element, said light emitting active layer structure is in direct contact with said second element first side, and said first element is in direct contact with said light emitting active layer structure.

68. A device as recited in claim 61, further comprising a second element, wherein said second element is positioned on said light emitting active layer structure, and said first element is positioned on said second element.

69. A solid state light emitting device as recited in claim 61, wherein the light emitting device further comprises at least a first reflective element, at least a portion of the light emitting active layer structure between the first reflective element and the first element.

70. A solid state light emitting device comprising:

a first element;

at least one light emitting active layer structure, said first element on said light emitting active layer structure; and

at least one second structure selected from (1) at least one lumiphor and (2) at least one encapsulant region,

said first element between said active layer structure and said second structure,

a second surface of said second structure facing said first element, a first region of said second structure comprising at least a portion of said second surface of said second structure, said first region of said second structure having a second structure first region index of refraction,

a first surface of said light emitting active layer structure facing said first element, a first region of said light emitting active layer structure comprising at least a portion of said first surface of said light emitting active layer structure, said first region of said light emitting active layer structure having an active layer first region index of refraction,

at least a first region of said first element having an index of refraction gradient, said index of refraction gradient ranging from a lower value to an upper value, said upper value not greater than said active layer first region index of refraction, said lower value lower than said upper value, but greater than said second structure first region index of refraction.

71. A device as recited in claim 70, further comprising a second element, said first element on said active layer first surface, said active layer second surface on said second element.

72. A device as recited in claim 71, further comprising at least one reflective element positioned between said second element and said light emitting active layer structure.

73. A device as recited in claim 71, further comprising at least one reflective element, said second element having a second element first side and a second element second side, said light emitting active layer on said second element first side, said reflective element on said second element second side.

74. A device as recited in claim 73, further comprising at least one bevel reflective element, said bevel reflective element on a second element third side, said second element third side extending between said second element first side and said second element second side.

75. A device as recited in claim 74, wherein said second element second side is in direct contact with said reflective element, said light emitting active layer structure is in direct contact with said second element first side, and said first element is in direct contact with said light emitting active layer structure.

76. A device as recited in claim 70, further comprising a second element, wherein said second element is positioned on said light emitting active layer structure, and said first element is positioned on said second element.

77. A solid state light emitting device as recited in claim 70, wherein the light emitting device further comprises at least a first reflective element, at least a portion of the light emitting active layer structure between the first reflective element and the first element.

78. A solid state light emitting device comprising:

at least one light emitting active layer structure, said light emitting active layer structure having an active layer structure first surface and an active layer structure second surface, a first region of said light emitting active layer structure which includes at least a portion of said active layer structure first surface having an active layer first region index of refraction; and

a first element on said active layer structure first surface;

said first surface of said light emitting active layer structure facing said first element,

said first element having a first element first surface and a first element second surface, said first element second surface on said active layer structure first surface, said first element first surface exposed to an exterior of said solid state lighting device,

at least a portion of said first element having an index of refraction gradient that ranges from at least 1.0 to a value that is less than said active layer first region index of refraction.

79. A device as recited in claim 78, further comprising a second element, said first element on said active layer first surface, said active layer second surface on said second element.

80. A device as recited in claim 79, further comprising at least one reflective element positioned between said second element and said light emitting active layer structure.

81. A device as recited in claim 79, further comprising at least one reflective element, said second element having a second element first side and a second element second side, said light emitting active layer on said second element first side, said reflective element on said second element second side.

82. A device as recited in claim 81, further comprising at least one bevel reflective element, said bevel reflective element on a second element third side, said second element third side extending between said second element first side and said second element second side.

83. A device as recited in claim 82, wherein said second element second side is in direct contact with said reflective element, said light emitting active layer structure is in direct contact with said second element first side, and said first element is in direct contact with said light emitting active layer structure.

84. A device as recited in claim 78, further comprising a second element, wherein said second element is positioned on said light emitting active layer structure, and said first element is positioned on said second element.

85. A solid state light emitting device as recited in claim 78, wherein the light emitting device further comprises at least a first reflective element, at least a portion of the light emitting active layer structure between the first reflective element and the first element.

86. A solid state light emitting device comprising:

at least one light emitting active layer structure, said light emitting active layer structure having an active layer structure first surface and an active layer structure second surface, a first region of said light emitting active layer structure which includes at least a portion of said active layer structure first surface having an active layer first region index of refraction;

a first element on said active layer structure first surface; and

at least one second structure selected from (1) at least one lumiphor and (2) at least one encapsulant region,

said first element between said active layer structure and said second structure,

a second surface of said second structure facing said first element, a first region of said second structure comprising at least a portion of said second surface of said second structure, said first region of said second structure having a second structure first region index of refraction,

at least a first region of said first element having an index of refraction gradient, said index of refraction gradient ranging from a value that is less than said active layer first region index of refraction to a value that is at least said second structure first region index of refraction.

87. A device as recited in claim 86, further comprising a second element, said first element on said active layer first surface, said active layer second surface on said second element.

88. A device as recited in claim 87, further comprising at least one reflective element positioned between said second element and said light emitting active layer structure.

89. A device as recited in claim 88, further comprising at least one reflective element, said second element having a second element first side and a second element second side, said light emitting active layer on said second element first side, said reflective element on said second element second side.

90. A device as recited in claim 89, further comprising at least one bevel reflective element, said bevel reflective element on a second element third side, said second element third side extending between said second element first side and said second element second side.

91. A device as recited in claim 90, wherein said second element second side is in direct contact with said reflective element, said light emitting active layer structure is in direct contact with said second element first side, and said first element is in direct contact with said light emitting active layer structure.

92. A device as recited in claim 86, further comprising a second element, wherein said second element is positioned on said light emitting active layer structure, and said first element is positioned on said second element.

93. A solid state light emitting device as recited in claim 86, wherein the light emitting device further comprises at least a first reflective element, at least a portion of the light emitting active layer structure between the first reflective element and the first element.