Light emitting diodes including modifications for light extraction

• US 6,791,119 B2
• Filed: 01/25/2002
• Issued: 09/14/2004
• Est. Priority Date: 02/01/2001
• Status: Expired due to Term

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Swoboda, Charles M., Keller, Bernd, Tarsa, Eric J., Thibeault, Brian, Glass, Robert C., Slater, David B. Jr.
• Primary Examiner(s): JACKSON JR, JEROME
• Application Number:
  US10/057,821
• Publication Number:
  US 20020123164A1
• Time in Patent Office: 963 Days
• Field of Search: 257/95, 257/98, 257/99
• US Class Current: 257/99
• CPC Class Codes: H01L 2224/32014 the layer connector being smaller than the bonding area, e.g. bond pad
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• 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 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/10253 Silicon [Si]
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Light emitting diodes include a substrate having first and second opposing faces and that is transparent to optical radiation in a predetermined wavelength range and that is patterned to define, in cross-section, a plurality of pedestals that extend into the substrate from the first face towards the second face. A diode region on the second face is configured to emit light in the predetermined wavelength range, into the substrate upon application of voltage across the diode region. A mounting support on the diode region, opposite the substrate is configured to support the diode region, such that the light that is emitted from the diode region into the substrate, is emitted from the first face upon application of voltage across the diode region. The first face of the substrate may include therein a plurality of grooves that define the plurality of triangular pedestals in the substrate. The grooves may include tapered sidewalls and/or a beveled floor. The first face of the substrate also may include therein an array of via holes. The via holes may include tapered sidewalls and/or a floor.

Claims

1. A light emitting diode comprising:

a substrate having first and second opposing faces, the first face having smaller surface area than the second face;

a diode region on the second face;

a first ohmic layer on the first face opposite the diode region;

an adhesion layer on the first ohmic layer opposite the substrate;

a first barrier layer on the adhesion layer opposite the first ohmic layer;

a first bonding layer on the first barrier layer opposite the adhesion layer;

a second ohmic layer on the diode region opposite the substrate;

a reflector layer on the second ohmic layer, opposite the diode region;

a second barrier layer on the reflector layer opposite the second ohmic layer; and

a second bonding layer on the second barrier layer opposite the reflector layer.

2. A light emitting diode according to claim 1 further comprising a mounting support on the second bonding layer opposite the second barrier layer.

3. A light emitting diode according to claim 1 wherein the second ohmic layer comprises a second ohmic and reflector layer.

4. A light emitting diode according to claim 1 wherein the first ohmic layer comprises a reflective metal.

5. A light emitting diode according to claim 1 wherein the adhesion layer comprises titanium.

6. A light emitting diode according to claim 1 wherein the first barrier layer comprises platinum.

7. A light emitting diode according to claim 1 wherein the first bonding layer comprises gold.

8. A light emitting diode according to claim 1 wherein the second ohmic layer comprises nickel/gold, nickel oxide/gold, nickel oxide/platinum, titanium and/or titanium/gold.

9. A light emitting diode according to claim 1 wherein the reflector layer comprises silver and/or aluminum.

10. A light emitting diode according to claim 1 wherein the second barrier layer comprises nickel, nickel/vanadium and/or titanium/tungsten.

11. A light emitting diode according to claim 1 wherein the second bonding layer comprises gold, indium, solder and/or braze.

12. A light emitting diode according to claim 1 wherein the first ohmic layer, the adhesion layer, the first barrier layer and the first bonding layer each comprises a central portion and at least one finger that extends from the central portion.

28. A light emitting diode according to claim 1:

wherein the substrate comprises a compensated, colorless silicon carbide substrate having first and second opposing faces; and

wherein the diode region comprises a gallium nitride-based diode region on the second face that is configured to emit light into the substrate upon application of voltage across the diode region.

29. A light emitting diode according to claim 28 further comprising:

a mounting support on the diode region, opposite the substrate, the mounting support being configured to support the diode region such that the light that is emitted from the diode region into the substrate, is emitted from the substrate, upon application of voltage across the diode region.

30. A light emitting diode according to claim 28 further comprising:

a mounting support on the first face, opposite the diode region, the mounting support being configured to support the first face.

31. A light emitting diode according to claim 29 wherein the reflector layer is configured to reflect light that is emitted from the diode region back into the diode region, through the substrate and from the substrate, upon application of voltage across the diode region.

32. A light emitting diode according to claim 30 further comprising:

a reflector between the mounting support and the first face, that is configured to reflect light that is emitted from the first face back into the substrate, upon application of voltage across the diode region.

33. A light emitting diode according to claim 31 further comprising:

a transparent electrode between the diode region and the reflector.

34. A light emitting diode according to claim 32 further comprising a transparent electrode between the first face and the reflector.

35. A light emitting diode according to claim 31 wherein the reflector layer comprises a layer of at least one reflective metal.

36. A light emitting diode according to claim 33 wherein the transparent electrode comprises a layer of nickel/gold, nickel oxide/gold, nickel oxide/platinum, titanium and/or titanium/gold.

37. A light emitting diode according to claim 31:

wherein the second barrier layer comprises a barrier region between the reflector layer and the mounting support; and

wherein the second bonding layer comprises a bonding region between the barrier region and the mounting support.

38. A light emitting diode according to claim 32:

wherein the first barrier layer comprises a barrier region between the reflector and the mounting support; and

wherein the first bonding layer comprises a bonding region between the barrier region and the mounting support.

39. A light emitting diode according to claim 37 wherein the bonding region comprises gold, indium, solder and/or braze.

40. A light emitting diode according to claim 38 wherein the bonding region comprises gold, indium, solder and/or braze.

41. A light emitting diode according to claim 28 further comprising:

an optical element adjacent the first face, opposite the diode region.

42. A light emitting diode according to claim 28 wherein the first face of the substrate includes therein at least one groove that defines, in cross-section, a plurality of pedestals that extend into the substrate from the first face towards the second face.

43. A light emitting diode according to claim 42 wherein the pedestals are triangular pedestals.

44. A light emitting diode according to claim 42 wherein the grooves include tapered and/or curved sidewalls.

45. A light emitting diode according to claim 42 wherein the grooves include a beveled and/or curved floor.

46. A light emitting diode according to claim 44 wherein the grooves include a beveled and/or curved floor.

47. A light emitting diode according to claim 42 wherein the first and second faces of the substrate comprise square perimeters.

48. A light emitting diode according to claim 42 wherein the first face of the substrate comprises a textured surface.

49. A light emitting diode according to claim 28 wherein the first face of the substrate includes therein an array of via holes that defines, in cross-section, a plurality of pedestals that extend into the substrate from the first face towards the second face.

50. A light emitting diode according to claim 49 wherein the via holes include tapered and/or curved sidewalls.

51. A light emitting diode according to claim 49 wherein the via holes include a flat, beveled and/or curved floor.

52. A light emitting diode according to claim 50 wherein the via holes include a flat, beveled and/or curved floor.

53. A light emitting diode according to claim 49 wherein the first and second faces of the substrate comprise square perimeters.

54. A light emitting diode according to claim 49 wherein the first face of the substrate comprises a textured surface.

55. A light emitting diode according to claim 49 wherein the array of via holes comprises an array of tapered and/or curved via holes.

56. A light emitting diode according to claim 28 wherein the diode region comprises a peripheral portion, at least one central portion that is enclosed by the peripheral portion and at least one emission region that is confined to within the at least one central portion and does not extend onto the peripheral portion.

57. A light emitting diode according to claim 28 further comprising:

a plurality of emission regions on the diode region, a respective one of which is confined to within a respective one of the pedestals and does not extend beyond the respective one of the pedestals.

58. A light emitting diode according to claim 42 further comprising:

a plurality of electrodes on the diode region, a respective one of which is confined to within a respective one of the pedestals and does not extend beyond the respective one of the pedestals.

59. A light emitting diode according to claim 49 further comprising:

at least one electrode on the diode region that does not overlap the via holes.

60. A light emitting diode according to claim 1:

wherein the first face is patterned to define, in cross-section, a plurality of pedestals that extend into the substrate from the first face towards the second face.

61. A light emitting diode according to claim 60 further comprising:

a mounting support on the diode region, opposite the substrate, the mounting support being configured to support the diode region such that the light that is emitted from the diode region into the substrate is emitted from the plurality of pedestals, upon application of voltage across the diode region.

62. A light emitting diode according to claim 60 further comprising:

a mounting support on the first face, opposite the diode region, the mounting support being configured to support the first face.

63. A light emitting diode according to claim 61 wherein the reflector layer is configured to reflect light that is emitted from the diode region back into the diode region, through the substrate that is transparent to optical radiation in the predetermined wavelength range and from the plurality of pedestals, upon application of voltage across the diode region.

64. A light emitting diode according to claim 62 further comprising:

a reflector between the mounting support and the first face, that is configured to reflect light that is emitted from the first face back into the substrate, upon application of voltage across the diode region.

65. A light emitting diode according to claim 63 further comprising:

a transparent electrode between the diode region and the reflector.

66. A light emitting diode according to claim 64 further comprising a transparent electrode between the first face and the reflector.

67. A light emitting diode according to claim 63 wherein the reflector layer comprises a layer of at least one reflective metal.

68. A light emitting diode according to claim 65 wherein the transparent electrode comprises a layer of nickel/gold, nickel oxide/gold, nickel oxide/platinum, titanium and/or titanium/gold.

69. A light emitting diode according to claim 63:

wherein the second barrier layer comprises a barrier region between the reflector layer and the mounting support; and

wherein the second bonding layer comprises a bonding region between the barrier region and the mounting support.

70. A light emitting diode according to claim 64:

wherein the first barrier layer comprises a barrier region between the reflector and the mounting support; and

wherein the first bonding layer comprises a bonding region between the barrier region and the mounting support.

71. A light emitting diode according to claim 69 wherein the bonding region comprises gold, indium, solder and/or braze.

72. A light emitting diode according to claim 70 wherein the bonding region comprises gold, indium, solder and/or braze.

73. A light emitting diode according to claim 60 further comprising:

an optical element adjacent the first face, opposite the diode region.

74. A light emitting diode according to claim 60 wherein the first face of the substrate includes therein at least one groove that defines, in cross-section, the plurality of pedestals in the substrate.

75. A light emitting diode according to claim 74 wherein the pedestals are triangular pedestals.

76. A light emitting diode according to claim 74 wherein the grooves include tapered and/or curved sidewalls.

77. A light emitting diode according to claim 74 wherein the grooves include a beveled and/or curved floor.

78. A light emitting diode according to claim 76 wherein the grooves include a beveled and/or curved floor.

79. A light emitting diode according to claim 74 wherein the first and second faces of the substrate comprise square perimeters.

80. A light emitting diode according to claim 74 wherein the first face of the substrate comprises a textured surface.

81. A light emitting diode according to claim 1 wherein the first face of the substrate includes therein an array of via holes that defines, in cross-section, the plurality of pedestals in the substrate.

82. A light emitting diode according to claim 81 wherein the via holes include tapered and/or curved sidewalls.

83. A light emitting diode according to claim 81 wherein the via holes include a flat, beveled and/or curved floor.

84. A light emitting diode according to claim 82 wherein the via holes include a flat, beveled and/or curved floor.

85. A light emitting diode according to claim 81 wherein the first and second faces of the substrate comprise square perimeters.

86. A light emitting diode according to claim 81 wherein the first face of the substrate comprises a textured surface.

87. A light emitting diode according to claim 81 wherein the array of via holes comprises an array of tapered and/or curved via holes.

88. A light emitting diode according to claim 60 wherein the diode region comprises a peripheral portion, at least one central portion that is enclosed by the peripheral portion and at least one emission region that is confined to within the at least one central portion and does not extend onto the peripheral portion.

89. A light emitting diode according to claim 60 further comprising:

a plurality of emission regions on the diode region, a respective one of which is confined to within a respective one of the pedestals and does not extend beyond the respective one of the pedestals.

90. A light emitting diode according to claim 74 further comprising:

a plurality of electrodes on the diode region, a respective one of which is confined to within a respective one of the pedestals and does not extend beyond the respective one of the pedestals.

91. A light emitting diode according to claim 81 further comprising:

at least one electrode on the diode region that does not overlap the via holes.

92. A light emitting diode according to claim 60, wherein the substrate comprises silicon carbide and wherein the diode region comprises gallium nitride.

93. A light emitting diode according to claim 60 wherein the first face has smaller surface area than the second face;

and

the diode region includes an emission region that is confined to within the smaller surface area of the first face.

94. A light emitting diode according to claim 93 wherein the emission region comprises a mesa.

95. A light emitting diode according to claim 93 wherein the first face of the substrate comprises a textured surface.

97. A light emitting diode according to claim 93 wherein the substrate is a silicon carbide substrate that is transparent to optical radiation in a predetermined wavelength range and wherein the diode region is configured to emit light in the predetermined wavelength range.

98. A light emitting diode according to claim 1 wherein the first face has smaller surface area than the second face;

the light emitting diode further comprising a mounting support on the diode region, opposite the substrate.

99. A light emitting diode according to claim 98 wherein the substrate is transparent to optical radiation in a predetermined wavelength range and wherein the diode region is configured to emit light in the predetermined wavelength range into the substrate that is transparent to the optical radiation in the predetermined wavelength range, upon application of voltage across the diode region.

100. A light emitting diode according to claim 99 wherein the mounting support is further configured to support the diode region such that the light that is emitted from the diode region into the substrate that is transparent to optical radiation in the predetermined wavelength range, is emitted from the first face, upon application of voltage across the diode region.

101. A light emitting diode according to claim 100 wherein the reflector layer is configured to reflect light that is emitted from the diode region back into the diode region, through the substrate that is transparent to optical radiation in the predetermined wavelength range and from the first face, upon application of voltage across the diode region.

102. A light emitting diode according to claim 101 further comprising:

a transparent electrode between the diode region and the reflector layer.

103. A light emitting diode according to claim 101 further comprising:

wherein the second barrier layer is between the reflector layer and the mounting support; and

wherein the second bonding layer is between the barrier layer and the mounting support.

104. A light emitting diode according to claim 103 wherein the bonding region comprises gold, indium, solder and/or braze.

13. A light emitting diode comprising:

a substrate having first and second opposing faces, the first face having smaller surface area than the second face;

a diode region on the second face;

a first layer comprising silver and/or aluminum on the first face opposite the diode region;

a second layer comprising titanium on the first layer opposite the substrate;

a third layer comprising platinum on the second layer opposite the first layer;

a fourth layer comprising gold on the third layer opposite the second layer;

a fifth layer comprising nickel/gold, nickel oxide/gold, nickel oxide/platinum, titanium and/or titanium/gold on the diode region opposite the substrate;

a sixth layer comprising silver and/or aluminum on the fifth layer, opposite the diode region;

a seventh layer comprising nickel, nickel/vanadium and/or titanium/tungsten on the sixth layer opposite the fifth layer; and

a eighth layer comprising gold, indium, solder and/or braze on the seventh layer opposite the sixth layer.

14. A light emitting diode according to claim 13 further comprising a mounting support on the eighth layer opposite the seventh layer.

15. A light emitting diode comprising:

a substrate having first and second opposing faces, the first face having smaller surface area than the second face;

a diode region on the second face;

a first adhesion layer on the first face opposite the diode region;

a first barrier layer on the first adhesion layer opposite the substrate;

a first bonding layer on the first barrier layer opposite the first adhesion layer;

an ohmic layer on the diode region opposite the substrate;

a reflector layer on the ohmic layer opposite the diode region;

a second adhesion layer on the reflector layer opposite the ohmic layer;

a second barrier layer on the second adhesion layer opposite the reflector layer; and

a second bonding layer on the second barrier layer opposite the second adhesion layer.

16. A light emitting diode according to claim 15 further comprising a mounting support on the first bonding layer opposite the first barrier layer.

17. A light emitting diode according to claim 15 wherein the ohmic layer comprises an ohmic and reflector layer.

18. A light emitting diode according to claim 15 wherein the first adhesion layer comprises titanium.

19. A light emitting diode according to claim 15 wherein the first barrier layer comprises platinum.

20. A light emitting diode according to claim 15 wherein the first bonding layer comprises gold.

21. A light emitting diode according to claim 15 wherein the ohmic layer comprises nickel/gold, nickel oxide/gold, nickel oxide/platinum, titanium and/or titanium/gold.

22. A light emitting diode according to claim 15 wherein the reflector layer comprises silver and/or aluminum.

23. A light emitting diode according to claim 15 wherein the second adhesion layer comprises titanium.

24. A light emitting diode according to claim 15 wherein the second barrier layer comprises platinum.

25. A light emitting diode according to claim 15 wherein the second bonding layer comprises gold.

27. A light emitting diode according to claim 25 further comprising a mounting support on the third layer opposite the second layer.

26. A light emitting diode comprising;

a substrate having first and second opposing faces, the first face having smaller surface area than the second face;

a diode region on the second face;

a first layer comprising titanium on the first face opposite the diode region;

a second layer comprising platinum on the first layer opposite the substrate;

a third layer comprising gold on the second layer opposite the first layer;

a fourth layer comprising nickel/gold, nickel oxide/gold, nickel oxide/platinum, titanium and/or titanium/gold on the diode region opposite the substrate;

a fifth layer comprising silver and/or aluminum on the fourth layer opposite the diode region;

a sixth layer comprising titanium on the fifth layer opposite the fourth layer;

a seventh layer comprising platinum on the sixth layer opposite the fifth layer; and

an eighth layer comprising gold on the seventh layer opposite the sixth layer.

96. A light emitting diode according to claim further comprising a transparent electrode on at least a portion of the mesa.