Group III nitride based light emitting diode structures with a quantum well and superlattice, group III nitride based quantum well structures and group III nitride based superlattice structures

• US 20030006418A1
• Filed: 05/07/2002
• Published: 01/09/2003
• Est. Priority Date: 05/30/2001
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: OʼLoughlin, Michael John, Ibbetson, James, Bergmann, Michael John, Emerson, David Todd, Doverspike, Kathleen Marie, Abare, Amber Christine, Nordby, Howard Dean Jr.
• Granted Patent: US 6,958,497 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/02378 Silicon carbide
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02505 consisting of more than two layers
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A light emitting diode is provided having a Group III nitride based superlattice and a Group III nitride based active region on the superlattice. The active region has at least one quantum well structure. The quantum well structure includes a first Group III nitride based barrier layer, a Group III nitride based quantum well layer on the first barrier layer and a second Group III nitride based barrier layer. A Group III nitride based semiconductor device and methods of fabricating a Group III nitride based semiconductor device having an active region comprising at least one quantum well structure are provided. The quantum well structure includes a well support layer comprising a Group III nitride, a quantum well layer comprising a Group III nitride on the well support layer and a cap layer comprising a Group III nitride on the quantum well layer. A Group III nitride based semiconductor device is also provided that includes a gallium nitride based superlattice having at least two periods of alternating layers of In_XGa_1−XN and In_YGa_1−YN, where 0≦X<1 and 0≦Y<1 and X is not equal to Y. The semiconductor device may be a light emitting diode with a Group III nitride based active region. The active region may be a multiple quantum well active region.

Claims

1. A Group III nitride based light emitting diode, comprising:

a Group III nitride based superlattice; and

a Group III nitride based active region on the superlattice comprising at least one quantum well structure comprising;

a first Group III nitride based barrier layer;

a Group III nitride based quantum well layer on the first barrier layer; and

a second Group III nitride based barrier layer on the Group III nitride based quantum well layer.

2. The light emitting diode of claim 1, wherein the at least one quantum well structure comprises from about 2 to about 10 repetitions of the at least one quantum well structure.

3. The light emitting diode of claim 1, wherein the superlattice comprises:

a gallium nitride based superlattice having at least two periods of alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N, where 0≦

X<

1 and 0≦

Y<

1 and X is not equal to Y;

wherein the first Group III nitride based barrier layer comprises a well support layer comprising a Group III nitride; and

wherein the second Group III nitride based barrier layer comprises a cap layer comprising a Group III nitride on the quantum well layer.

4. The light emitting diode according to claim 3, wherein the cap layer has a lower crystal quality than the well support layer.

5. The light emitting diode according to claim 3, wherein the well support layer comprises a gallium nitride based layer, the quantum well layer comprises an indium gallium nitride layer and the barrier layer comprises a gallium nitride based layer.

6. The light emitting diode according to claim 3, wherein the well support layer and the cap layer comprises a layer of In_XGa₁₋

XN where 0≦

X<

1.

7. The light emitting diode according to claim 6, wherein an indium composition of the well support layer and the cap layer is less an indium composition of the quantum well layer.

8. The light emitting diode according to claim 3, wherein the well support layer and the cap layer comprises a layer of Al_XIn_YGa₁₋

X−

YN where 0<

X<

1, 0≦

Y<

1 and X+Y≦

1.

9. The light emitting diode according to claim 8, wherein X≦

Y+0.05.

10. The light emitting diode according to claim 3, wherein the well support layer and the cap layer are undoped.

11. The light emitting diode according to claim 3, wherein the well support layer and the cap layer have a doping level of less than about 5×

10¹⁹ cm<sup>−

3</sup>.

12. The light emitting diode according to claim 3, wherein the cap layer and the well support layer have a higher bandgap than the quantum well layer.

13. The light emitting diode according to claim 3, wherein a combined thickness of the well support layer and the cap layer is from about 50 to about 400 Å

.

14. The light emitting diode according to claim 3, wherein a thickness of the well support layer is greater than a thickness of the cap layer.

15. The light emitting diode according to claim 3, wherein the quantum well layer has a thickness of from about 10 to about 50 Å

.

16. The light emitting diode according to claim 3, wherein the quantum well layer has a thickness of about 25 Å

.

17. The light emitting diode according to claim 3, wherein a percentage of indium in the quantum well layer is from about 5% to about 50% .

18. The light emitting diode according to claim 3, further comprising a Group III nitride based spacer layer between the well support layer and the superlattice.

19. The light emitting diode according to claim 18, wherein the spacer layer comprises undoped GaN.

20. The light emitting diode according to claim 3, wherein a bandgap of the at least one quantum well is less than a bandgap of the superlattice.

21. The light emitting diode according to claim 3, further comprising:

a second well support layer comprising a Group III nitride on the cap layer;

a second quantum well layer comprising a Group III nitride on the second well support layer; and

a second cap layer comprising a Group III nitride on the second quantum well layer.

22. The light emitting diode according to claim 3, wherein the gallium nitride based superlattice comprises from about 5 to about 50 periods.

23. The light emitting diode according to claim 3, wherein layers of In_XGa₁₋

XN and In_YGa<sub>1−

Y</sub>N of the alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N have a combined thickness of less than about 70 Å

.

24. The light emitting diode according to claim 3, wherein X=0.

25. The light emitting diode according to claim 24, wherein InGaN layers of the alternating layers of In_XGa₁₋

XN and In_YGa<sub>1−

Y</sub>N have a thickness of from about 5 to about 40 Å and

GaN layers of the alternating layers of InGa_1-XN and In_YGa_1-YN have a thickness of from about 5 to about 100 Å

.

26. The light emitting diode according to claim 24, wherein InGaN layers of the alternating layers of In_XGa₁₋

XN and In_YGa<sub>1−

Y</sub>N have a thickness of about 15 Å and

GaN layers of the alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N have a thickness of from about 30 Å

.

27. The light emitting diode according to claim 3, wherein the gallium nitride based superlattice is doped with an n-type impurity to a level of from about 1×

10¹⁷ cm<sup>−

3</sup> to about 5×

10¹⁹ cm<sup>−

3</sup>.

28. The light emitting diode according to claim 27, wherein the doping level of the gallium nitride based superlattice is an actual doping level of layers of the alternating layers.

29. The light emitting diode according to claim 27, wherein the doping level is an average doping level of layers of the alternating layers.

30. The light emitting diode according to claim 3, further comprising doped Group III nitride layers adjacent the superlattice and wherein the doped Group III nitride layers are doped with an n-type impurity to provide an average doping of the doped Group III nitride layers and the superlattice of from about 1×

10¹⁷ cm<sup>−

3</sup> to about 5×

10¹⁹cm<sup>−

3</sup>.

31. The light emitting diode according to claim 3, wherein a bandgap of the superlattice is from about 2.95 eV to about 3.35 eV.

32. The light emitting diode according to claim 3, wherein a bandgap of the superlattice is about 3.15 eV.

33. A Group III nitride based semiconductor device having an active region comprising at least one quantum well structure, the quantum well structure comprising:

a well support layer comprising a Group III nitride;

a quantum well layer comprising a Group III nitride on the well support layer; and

a cap layer comprising a Group III nitride on the quantum well layer.

34. The Group III nitride based device according to claim 33, wherein the cap layer has a lower crystal quality than the well support layer.

35. The Group III nitride based semiconductor device according to claim 33, wherein the well support layer comprises a gallium nitride based layer, the quantum well layer comprises an indium gallium nitride layer and the barrier layer comprises a gallium nitride based layer.

36. The Group III nitride based semiconductor device according to claim 35, wherein the well support layer and the cap layer comprises a layer of In_XGa₁₋

XN where 0≦

X<

1.

37. The Group III nitride based semiconductor device according to claim 36, wherein an indium composition of the well support layer and the cap layer is less an indium composition of the quantum well layer.

38. The Group III nitride based semiconductor device according to claim 35, wherein the well support layer and the cap layer comprises a layer of Al_XIn_YG₁₋

X−

YN where 0<

X<

1, 0≦

Y<

1 and X+Y≦

1.

39. The Group III nitride based semiconductor device according to claim 38, wherein X≦

Y+0.05.

40. The Group III nitride based semiconductor device according to claim 35, wherein the well support layer and the cap layer are undoped.

41. The Group III nitride based semiconductor device according to claim 35, wherein the well support layer and the cap layer have a doping level of less than about 5×

10¹⁹ cm<sup>−

3</sup>.

42. The Group III nitride based semiconductor device according to claim 33, wherein the cap layer and the well support layer have a higher bandgap than the quantum well layer.

43. The Group III nitride based semiconductor device according to claim 35, wherein a combined thickness of the well support layer and the cap layer is from about 50 to about 400 Å

.

44. The Group III nitride based semiconductor device according to claim 35, wherein a combined thickness of the well support layer and the cap layer is greater than about 90 Å

.

45. The Group III nitride based semiconductor device according to claim 35, wherein a combined thickness of the well support layer and the cap layer is about 225 Å

.

46. The Group III nitride based semiconductor device according to claim 35, wherein a thickness of the well support layer is greater than a thickness of the cap layer.

47. The Group III nitride based semiconductor device according to claim 35, wherein the quantum well layer has a thickness of from about 10 to about 50 Å

.

48. The Group III nitride based semiconductor device according to claim 35, wherein the quantum well layer has a thickness of about 25 Å

.

49. The Group III nitride based semiconductor device according to claim 35, wherein a percentage of indium in the quantum well layer is from about 5% to about 50%.

50. The Group III nitride based semiconductor device according to claim 35, further comprising a superlattice and wherein the well support layer is on the superlattice.

51. The Group III nitride based semiconductor device according to claim 50, wherein a bandgap of the superlattice is from about 2.95 to about 3.35 eV.

52. The Group III nitride based semiconductor device according to claim 50, wherein a bandgap of the superlattice is about 3.15 eV.

53. The Group III nitride based semiconductor device according to claim 50, further comprising a Group III nitride based spacer layer between the well support layer and the superlattice.

54. The Group III nitride based semiconductor device according to claim 53, wherein the spacer layer comprises undoped GaN.

55. The Group III nitride based semiconductor device according to claim 50, wherein a bandgap of the at least one quantum well is less than a bandgap of the superlattice.

56. The Group III nitride based semiconductor device according to claim 33, further comprising:

a second well support layer comprising a Group III nitride on the cap layer;

a second quantum well layer comprising a Group III nitride on the second well support layer; and

a second cap layer comprising a Group III nitride on the second quantum well layer.

57. The Group III nitride based semiconductor device according to claim 33 having from about 2 to about 10 repetitions of the at least one quantum well structures.

59. The Group III nitride based semiconductor device according to claim 58, wherein the gallium nitride based superlattice comprises from about 5 to about 50 periods.

60. The Group III nitride based semiconductor device according to claim 58, wherein the gallium nitride based superlattice comprises 25 periods.

61. The Group III nitride based semiconductor device according to claim 58, wherein the gallium nitride based superlattice comprises 10 periods.

62. The Group III nitride based semiconductor device according to claim 58, wherein layers of In_XGa₁₋

XN and In_YGa<sub>1−

Y</sub>N of the alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N have a combined thickness of less than about 70 Å

.

63. The Group III nitride based semiconductor device according to claim 58, wherein X=0.

64. The Group III nitride based semiconductor device according to claim 63, wherein InGaN layers of the alternating layers of In_XGa₁₋

XN and In_YGa<sub>1−

Y</sub>N have a thickness of from about 5 to about 40 Å and

GaN layers of the alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N have a thickness of from about 5 to about 100 Å

.

65. The Group III nitride based semiconductor device according to claim 63, wherein InGaN layers of the alternating layers of In_XGa₁₋

XN and In_YGa<sub>1−

Y</sub>N have a thickness of about 15 Å and

GaN layers of the alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N have a thickness of from about 30 Å

.

66. The Group III nitride based semiconductor device according to claim 58, wherein the gallium nitride based superlattice is doped with an n-type impurity to a level of from about 1×

10¹⁷ cm<sup>−

3</sup> to about 5×

10¹⁹ cm<sup>−

3</sup>.

67. The Group III nitride based semiconductor device according to claim 66, wherein the doping level of the gallium nitride based superlattice is an actual doping level of layers of the alternating layers.

68. The Group III nitride based semiconductor device according to claim 66, wherein the doping level is an average doping level of layers of the alternating layers.

69. The Group III nitride based semiconductor device according to claim 58, further comprising doped Group III nitride layers adjacent the superlattice and wherein the doped Group III nitride layers are doped with an n-type impurity to provide an average doping of the doped Group III nitride layers and the superlattice of from about 1 ×

10¹⁷ cm<sup>−

3</sup> to about 5×

10¹⁹cm<sup>−

3</sup>.

70. The Group III nitride based semiconductor device according to claim 58, wherein a bandgap of the superlattice is about 3.15 eV.

71. The Group III nitride based semiconductor device according to claim 58, wherein a bandgap of the superlattice is from about 2.95 to about 3.15 eV.

72. The Group III nitride based semiconductor device according to claim 58, wherein the semiconductor device comprises a light emitting diode, the light emitting diode further comprising a Group III nitride based active region on the superlattice.

73. The Group III nitride based semiconductor device according to claim 72, further comprising a Group III nitride based spacer layer between the active region and the superlattice.

74. The Group III nitride based semiconductor device according to claim 73, wherein the spacer layer comprises undoped GaN.

75. The Group III nitride based semiconductor device according to claim 72, wherein the active region comprises at least one quantum well.

76. The Group III nitride based semiconductor device according to claim 75, wherein a bandgap of the at least one quantum well is less than a bandgap of the superlattice.

58. A Group III nitride based semiconductor device, comprising:

a gallium nitride based superlattice having at least two periods of alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N, where 0≦

X<

1 and 0≦

Y <

1 and X is not equal to Y.

77. A gallium nitride based light emitting diode, comprising:

a gallium nitride based superlattice having at least two periods of alternating layers of In_XGa<sub>1−

X</sub>N and In_YGa<sub>1−

Y</sub>N, where 0≦

X<

1 and 0≦

Y<

1 and X is not equal to Y; and

a gallium nitride based active region on the gallium nitride based superlattice.

78. The gallium nitride based light emitting diode of claim 77, wherein a bandgap of the gallium nitride based active region is less than a bandgap of the superlattice.

80. The method of claim 79, wherein the step of forming a well support layer comprising a Group III nitride comprises forming the well support layer at a first temperature;

wherein the step of forming a quantum well layer comprises forming the quantum well layer at a second temperature which is less than the first temperature; and

wherein the step of forming a cap layer comprises forming the cap layer at a third temperature which is less than the first temperature.

81. The method of claim 80, wherein the third temperature is substantially the same as the second temperature.

82. The method of claim 81, wherein the well support layer comprises a gallium nitride based layer, the quantum well layer comprises an indium gallium nitride layer and the cap layer comprises a gallium nitride based layer.

83. The method of claim 82, wherein the first temperature is from about 700 to about 900°

C.

84. The method of claim 82, wherein the second temperature is from about 0 to about 200°

C. less than the first temperature.

85. The method of claim 82, wherein the second temperature is less that the first temperature.

86. The method of claim 82, wherein the indium gallium nitride layer is formed in a nitrogen atmosphere.

87. The method of claim 82, wherein the steps of forming a well support layer and forming a cap layer comprise forming a cap layer of In_XGa₁₋

XN, where 0≦

X<

1 and forming a well support layer of In_XGa<sub>1−

X</sub>N, where 0≦

X<

1.

88. The method of claim 87, wherein an indium composition of the well support layer and the cap layer is less an indium composition of the quantum well layer.

89. The method of claim 82, wherein the steps of forming a well support layer and forming a cap layer comprise forming a cap layer of Al_XIn_YGa₁₋

X−

YN, where 0<

X<

1, 0≦

Y<

1 and X+Y≦

1 and forming a well support layer of Al_XIn_YGa<sub>1−

X−

Y</sub>N, where 0<

X<

1, 0≦

Y<

1 and X+Y≦

1.

90. The method of claim 89, wherein X≦

Y+0.05.

91. The method of claim 82, wherein the well support layer and the cap layer are undoped.

92. The method of claim 82, wherein the well support layer and the cap layer have a doping level of less than about 5×

10¹⁹ cm<sup>−

3</sup>.

93. The method of claim 79, wherein the cap layer and the well support layer have a higher bandgap than the quantum well layer.

94. The method of claim 82, wherein a combined thickness of the well support layer and the cap layer is from about 50 to about 400 Å

.

95. The method of claim 82, wherein a thickness of the well support layer is greater than a thickness of the cap layer.

96. The method of claim 82, wherein the quantum well layer has a thickness of from about 10 to about 50 Å

.

97. The method of claim 82, wherein a percentage of indium in the quantum well layer is from about 5% to about 50% .

98. The method of claim 82, further comprising the step of forming a superlattice, wherein the well support layer is on the superlattice.

99. The method of claim 98, further comprising the step of forming a Group III nitride based spacer layer between the well support layer and the superlattice.

100. The method of claim 99, wherein the spacer layer comprises undoped GaN.

101. The method of claim 98, wherein a bandgap of the quantum well layer is less than a bandgap of the superlattice.

102. The method of claim 79, further comprising:

forming a second well support layer comprising a Group III nitride on the cap layer;

forming a second quantum well layer comprising a Group III nitride on the second well support layer; and

forming a second cap layer comprising a Group III nitride on the second quantum well layer.

103. The method of claim 102, wherein the step of forming a second well support layer comprising a Group III nitride comprises forming the second well support layer at substantially the first temperature;

wherein the step of forming a second quantum well layer comprises forming the second quantum well layer at substantially the second temperature which is less than the first temperature; and

wherein the step of forming a second cap layer comprises forming the second cap layer at substantially the third temperature which is less than the first temperature.

104. The method of claim 103, wherein the third temperature is substantially the same as the second temperature.

105. The method of claim 80, further comprising forming from about 2 to about 10 repetitions of the at least one quantum well structures.

79. A method of fabricating a Group III nitride based semiconductor device having an active region comprising at least one quantum well structure, comprising:

forming a well support layer comprising a Group III nitride;

forming a quantum well layer comprising a Group III nitride on the quantum well support layer; and

forming a cap layer comprising a Group III nitride on the quantum well layer.