Light emitting diodes with low refractive index material layers to reduce light guiding effects

• US 9,269,876 B2
• Filed: 03/06/2013
• Issued: 02/23/2016
• Est. Priority Date: 03/06/2012
• Status: Active Grant

• Current Assignee: Korrus Incorporated (MKD Electric, Inc.)
• Original Assignee: Soraa, Inc.
• Inventors: David, Aurelien J. F., Grundmann, Michael J.
• Primary Examiner(s): Menz, Laura
• Assistant Examiner(s): Malek, Maliheh
• Application Number:
  US13/787,582
• Publication Number:
  US 20130234108A1
• Time in Patent Office: 1,084 Days
• Field of Search: 438/22, 438 26- 27, 438/29, 438/31, 438/34, 438 39- 41, 438 46- 47, 438/106, 438/116, 438118-120, 257/79, 257/91, 257/94, 257/95, 257/98, 257/99, 257/100, 257183-1831, 257/200, 257431-437, 257/678, 257/680, 257E33073-E33074, 257/E33.067
• US Class Current: 1/1
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: H01L 33/02 characterised by the semiconductor bodies
• CPC Class Codes: H01L 33/04 with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/58 Optical field-shaping elements

Abstract

Light emitting diodes including low refractive index layers for reducing guided light are disclosed. The light-emitting diodes include at least one n-doped layer, at least one p-doped layer, and an active region disposed between the at least one n-doped layer and the at least one p-doped layer. The active region comprises a light-emitting material. The light-emitting diode further comprises at least one low refractive index layer disposed in or around the active region.

Claims

1. A light-emitting diode (LED) comprising:

at least one n-doped layer ;

at least one p-doped layer;

an active region comprising of at least one layer of light-emitting material, disposed between the at least one n-doped layer and the at least one p-doped layer;

at least one low refractive index layer disposed within one optical wavelength of the active region, wherein the optical wavelength indicates wavelength of light emitted from the active region, and the at least one low refractive index layer configured to substantially reduce light guiding by the active region; and

an InGaN superlattice underlying the active region, wherein the at least one low refractive index material layer is disposed within less than one optical wavelength of the InGaN superlattice,

wherein the active region including the at least one low refractive index layer is characterized by an average refractive index from 0% to 5% higher than the refractive index of a host material.

2. The light-emitting diode of claim 1, wherein less than 10% of total light emitted by the light-emitting material is guided by the active region.

3. The light-emitting diode of claim 1, wherein less than 2% of total light emitted by the light-emitting material is guided by the active region.

4. The light-emitting diode of claim 1, further comprising an additional light-extracting feature.

5. The light-emitting diode of claim 1, wherein the LED comprises a Group III-nitride material characterized by a surface orientation selected from a non-polar crystallographic orientation and semipolar crystallographic orientation.

6. The light-emitting diode of claim 1, wherein the at least one low refractive index material layer comprises a non-homogeneous material composition.

7. The light-emitting diode of claim 1, wherein the at least one low refractive index material layer is configured as a carrier confinement layer.

8. The light-emitting diode of claim 1, wherein the active region is characterized by a cumulative thickness of at least 10 nm.

9. The light-emitting diode of claim 1, wherein the active region is characterized by a cumulative thickness less than 100 nm.

10. The light-emitting diode of claim 1, wherein the at least one low refractive index material layer is disposed on one side of the active region, on both sides of the active region, within the active region, or a combination of any of the foregoing.

11. The light-emitting diode of claim 1, wherein the active region comprises two or more quantum wells, wherein at least one barrier layer between the two or more quantum wells comprises a low refractive index material.

12. The light-emitting diode of claim 1, wherein the at least one low refractive index layer is substantially lattice matched or polarization matched to the host material of the light-emitting diode.

13. The light-emitting diode of claim 1, wherein the at least one low refractive index material layer is substantially lattice matched or polarization matched to the at least one layer of light emitting material.

14. The light-emitting diode of claim 1, wherein the active region comprises one or more double-heterostructure layers.

15. The light-emitting diode of claim 1, wherein additional material comprising low-composition quantum wells that do not emit a substantial amount of light, is grown above or below the active region.

16. The light-emitting diode of claim 1, wherein the LED is characterized by an emission wavelength from about 200 nm to about 1000 nm.

17. A light-emitting diode (LED) comprising:

at least one n-doped layer comprising a gallium-nitride-based material having a host refractive index;

at least one p-doped layer comprising a gallium-nitride-based material;

an AlGaN/InGaN superlattice characterized by an average refractive index, wherein the average refractive index does not exceed that of the host refractive index by more than 0.05;

an active region comprising a series of quantum wells, or one or more double heterostructures, wherein the series of quantum wells, or the one or more double heterostructures have a first indium composition, and further comprising a series of InGaN dummy quantum wells having a second indium composition lower than the first indium composition, wherein the dummy quantum wells do not emit a substantial amount of light and are positioned either above or below the active region, and wherein the active region is characterized by a total thickness of less than 50 nm; and

an electron blocking layer having a low refractive index, wherein the low refractive index is lower than the host refractive index by at least 0.05.

21. The light-emitting diode of claim 17, wherein less than 10% of total light emitted by the light-emitting material is guided by the active region.

22. The light-emitting diode of claim 17, wherein less than 2% of total light emitted by the light-emitting material is guided by the active region.

23. The light-emitting diode of claim 17, further comprising an additional light-extracting feature.

24. The light-emitting diode of claim 17, wherein the LED comprises a Group III-nitride material characterized by a surface orientation selected from a non-polar crystallographic orientation and semipolar crystallographic orientation.

25. The light-emitting diode of claim 17, wherein the at least one low refractive index material layer comprises a non-homogeneous material composition.

26. The light-emitting diode of claim 17, wherein the at least one low refractive index material layer is configured as a carrier confinement layer.

27. The light-emitting diode of claim 17, wherein the active region is characterized by a cumulative thickness of at least 10 nm.

28. The light-emitting diode of claim 17, wherein the active region is characterized by a cumulative thickness less than 100 nm.

29. The light-emitting diode of claim 17, wherein the at least one low refractive index material layer is disposed on one side of the active region, on both sides of the active region, within the active region, or a combination of any of the foregoing.

30. The light-emitting diode of claim 17, wherein the active region comprises two or more quantum wells, wherein at least one barrier layer between the two or more quantum wells comprises a low refractive index material.

31. The light emitting diode of claim 17, further comprising an InGaN superlattice underlying the active region, wherein the at least one low refractive index material layer is disposed within less than one optical wavelength of the InGaN superlattice, wherein the optical wavelength indicates wavelength of light emitted from the active region.

32. The light-emitting diode of claim 17, wherein the electron blocking layer is substantially lattice matched or polarization matched to a host material of the light-emitting diode.

33. The light-emitting diode of claim 17, wherein the electron blocking layer is substantially lattice matched or polarization matched to the light emitting material.

34. The light-emitting diode of claim 17, wherein the active region comprises one or more double-heterostructure layers.

35. The light-emitting diode of claim 17, wherein additional material comprising low-composition quantum wells that do not emit a substantial amount of light, is grown above or below the active region.

36. The light-emitting diode of claim 17, wherein the LED is characterized by an emission wavelength from about 200 nm to about 1000 nm.

18. A light-emitting diode (LED) comprising:

at least one n-doped layer comprising a gallium-nitride-based material;

at least one p-doped layer comprising a gallium-nitride-based material;

an active region disposed between the at least one n-doped layer and the at least one p-doped layer, the active region comprising one or more layers formed of an indium-gallium- nitride-based light emitting material;

at least one low refractive index material layer disposed between the at least one p-doped layer and the active region, or between the at least one n-doped layer and the active region, wherein the at least one low refractive index material layer has an index of refraction lower than an index of refraction of gallium nitride; and

an InGaN superlattice underlying the active region, wherein the at least one low refractive index material layer is disposed within less than one optical wavelength of the InGaN superlattice, wherein the optical wavelength indicates wavelength of light emitted from the active region.

19. The light-emitting diode device of claim 18, wherein the at least one low refractive index material layer is configured to substantially reduce light guiding by the active region.

37. The light-emitting diode of claim 18, wherein less than 10% of total light emitted by the light-emitting material is guided by the active region.

38. The light-emitting diode of claim 18, wherein less than 2% of total light emitted by the light-emitting material is guided by the active region.

39. The light-emitting diode of claim 18, further comprising an additional light-extracting feature.

40. The light-emitting diode of claim 18, wherein the LED comprises a Group III-nitride material characterized by a surface orientation selected from a non-polar crystallographic orientation and semipolar crystallographic orientation.

41. The light-emitting diode of claim 18, wherein the at least one low refractive index material layer comprises a non-homogeneous material composition.

42. The light-emitting diode of claim 18, wherein the at least one low refractive index material layer is configured as a carrier confinement layer.

43. The light-emitting diode of claim 18, wherein the active region is characterized by a cumulative thickness of at least 10 nm.

44. The light-emitting diode of claim 18, wherein the active region is characterized by a cumulative thickness less than 100 nm.

45. The light-emitting diode of claim 18, wherein the at least one low refractive index material layer is disposed on one side of the active region, on both sides of the active region, within the active region, or a combination of any of the foregoing.

46. The light-emitting diode of claim 18, wherein the active region comprises two or more quantum wells, wherein at least one barrier layer between the two or more quantum wells comprises a low refractive index material.

47. The light-emitting diode of claim 18, wherein the at least one low refractive index layer is substantially lattice matched or polarization matched to a host material of the light-emitting diode.

48. The light-emitting diode of claim 18, wherein the at least one low refractive index material layer is substantially lattice matched or polarization matched to the indium-gallium-nitride-based light emitting material.

49. The light-emitting diode of claim 18, wherein the active region comprises one or more double-heterostructure layers.

50. The light-emitting diode of claim 18, wherein additional material comprising low-composition quantum wells that do not emit a substantial amount of light, is grown above or below the active region.

51. The light-emitting diode of claim 18, wherein the LED is characterized by an emission wavelength from about 200 nm to about 1000 nm.

20. A method of fabricating a light-emitting diode (LED) comprising:

providing a substrate, the substrate including a surface region comprising a gallium- nitride-based material;

forming at least one n-doped layer coupled to the surface region of the substrate, the at least one n-doped layer comprising a gallium-nitride-based material;

forming an active region coupled to the n-doped layer, the active region comprising one or more layers formed of an indium-gallium-nitride-based material;

forming at least one p-doped layer coupled to the active region, the at least one p-doped layer comprising a gallium-nitride-based material;

forming at least one low refractive index material layer disposed between the at least one p-doped layer and the active region, or between the at least one n-doped layer and the active region, wherein the at least one low refractive index layer has an index of refraction lower than an index of refraction of gallium nitride and the low refractive index layer is formed to substantially reduce light guiding by the active region; and

forming an InGaN superlattice underlying the active region, wherein the at least one low refractive index material layer is disposed within less than one optical wavelength of the InGaN superlattice, wherein the optical wavelength indicates wavelength of light emitted from the active region.

52. The light-emitting diode of claim 20, wherein less than 10% of total light emitted by the light-emitting material is guided by the active region.

53. The light-emitting diode of claim 20, wherein less than 2% of total light emitted by the light-emitting material is guided by the active region.

54. The light-emitting diode of claim 20, further comprising an additional light-extracting feature.

55. The light-emitting diode of claim 20, wherein the LED comprises a Group III-nitride material characterized by a surface orientation selected from a non-polar crystallographic orientation and semipolar crystallographic orientation.

56. The light-emitting diode of claim 20, wherein the at least one low refractive index material layer comprises a non-homogeneous material composition.

57. The light-emitting diode of claim 20, wherein the at least one low refractive index material layer is configured as a carrier confinement layer.

58. The light-emitting diode of claim 20, wherein the active region is characterized by a cumulative thickness of at least 10 nm.

59. The light-emitting diode of claim 20, wherein the active region is characterized by a cumulative thickness less than 100 nm.

60. The light-emitting diode of claim 20, wherein the at least one low refractive index material layer is disposed on one side of the active region, on both sides of the active region, within the active region, or a combination of any of the foregoing.

61. The light-emitting diode of claim 20, wherein the active region comprises two or more quantum wells, wherein at least one barrier layer between the two or more quantum wells comprises a low refractive index material.

62. The light-emitting diode of claim 20, wherein the at least one low refractive index layer is substantially lattice matched or polarization matched to a host material of the light-emitting diode.

63. The light-emitting diode of claim 20, wherein the at least one low refractive index material layer is substantially lattice matched or polarization matched to the indium-gallium-nitride-based light emitting material.

64. The light-emitting diode of claim 20, wherein the active region comprises one or more double-heterostructure layers.

65. The light-emitting diode of claim 20, wherein additional material comprising low-composition quantum wells that do not emit a substantial amount of light, is grown above or below the active region.

66. The light-emitting diode of claim 20, wherein the LED is characterized by an emission wavelength from about 200 nm to about 1000 nm.