Light-emitting diode with silicon carbide substrate

• US 6,919,585 B2
• Filed: 05/17/2002
• Issued: 07/19/2005
• Est. Priority Date: 05/17/2002
• Status: Expired due to Term

• Current Assignee: Dalian Meiming Epitaxy Technology Co., Ltd.
• Original Assignee: Lumei Optoelectronics Incorporated
• Inventors: Liu, Heng
• Primary Examiner(s): JACKSON JR, JEROME
• Application Number:
  US10/147,078
• Publication Number:
  US 20030214807A1
• Time in Patent Office: 1,159 Days
• Field of Search: 257/99, 257/96, 257/97, 257/103
• US Class Current: 257/97
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A light-emitting diode is based on an undoped intrinsic SiC substrate on which are grown: an insulating buffer or nucleation structure; a light-emitting structure; window layers; a semi-transparent conductive layer; a bond pad adhesion layer; a p-type electrode bond pad; and an n-type electrode bond pad. In one embodiment, the light-emitting surface of the substrate is roughened to maximize light emission.

Claims

1. A light-emitting diode which emits light in the 400-550 nm portion of a visible spectrum, said light emitting diode comprising:

an undoped SIC substrate;

a nitride nucleating buffer structure disposed on an upper surface of said SiC substrate;

a p-n junction diode heterostructure disposed on said buffer structure, comprising;

a first cladding layer; and

a second cladding layer, said first cladding layer and said second cladding layer being comprised of one of binary Group III nitrides and ternary Group III nitrides;

a first window layer formed of Mg doped GaN and disposed on said p-n junction diode heterostructure;

a second window layer formed of Mg doped GaN and disposed on said first window layer;

a conductive layer formed of NiO/Au and disposed on said second window layer, an upper surface of said conductive layer being an upper surface of the light-emitting diode;

a first opening formed at one side of the light emitting diode and through said conductive layer such that a first bond pad is disposed on an upper surface of said second window layer;

a first electrode disposed on said first bond pad;

a second opening formed at another side of the light emitting diode, said second opening forming a three walled notch in said light emitting diode, said second opening being formed through to said first cladding layer on which a second bond pad is disposed; and

a second electrode disposed on said bond pad.

2. The light-emitting diode according to claim 1, wherein said buffer structure is chosen from gallium nitride, indium nitride, ternary Group III nitrides having a formula A_xB_1-xN where A and B are Group III elements and where x is one of zero, one, and a fraction between zero and one, quaternary Group III nitrides having a formula A_xB_yC_1-x-yN, where A, B, and C are Group III elements, x and y are one of zero, one, and a fraction between zero and one, and 1 is greater than a sum of x and y, and alloys of SiC with such ternary and quaternary Group III nitrides.

4. The light-emitting diode according to claim 1, wherein said buffer structure comprises a single layer of aluminum nitride.

6. The light-emitting diode according to claim 1, wherein a power output rating is at least 1 mW when operating with a driving current between said electrodes of 20 milliamps.

8. The light-emitting diode according to claim 1, wherein said p-n junction diode heterostructure comprises a double heterostructure, said double heterostructure comprising:

an active layer chosen from gallium nitride, aluminum nitride, indium nitride, ternary Group III nitrides having a formula A_xB_1-xN where A and B are Group III elements and where x is one of zero, one, and a fraction between zero and one, and alloys of gallium nitride with such ternary Group III nitrides, quaternary Group III nitrides having a formula A_xB_yC_1-x-yN, where A, B, and C are Group III elements and where x is one of zero, one, and a fraction between zero and one, y is one of zero, one, and a fraction between zero and one, a sum of x and y is less than one, and alloys of gallium nitride with such quarternary Group III nitrides.

15. The light-emitting diode according to claim 1, wherein said lower surface of said SiC substrate minimizes reflection back into said SiC substrate and said light-emitting structure.

16. The light-emitting diode according to claim 15, wherein an ohmic contact to said first cladding layer and an ohmic contact to said second cladding layer are each disposed at a side of said epitaxial layer.

17. The light-emitting diode according to claim 1, wherein said first cladding layer is formed of silicon doped gallium nitride.

18. The light-emitting diode according to claim 1, wherein said active layer is formed from a silicon doped n-type gallium indium nitride/gallium nitride multi-quantum well structure.

19. The light-emitting diode according to claim 1, wherein said second cladding layer is formed of magnesium doped aluminum gallium nitride.

20. The light-emitting diode according to claim 1, wherein said second window layer is formed of a relatively more highly doped magnesium gallium nitride than said first window layer.

21. The light-emitting diode according to claim 1, further comprising a reflective bond pad disposed on said first cladding layer.

3. A light-emitting diode which emits light in the 400-550 nm portion of a visible spectrum, said light emitting diode comprising:

an undoped SiC substrate;

a nitride nucleating buffer structure disposed on an upper surface of said SiC substrate;

a p-n junction diode heterostructure disposed on said buffer structure, comprising;

a first cladding layer; and

a second cladding layer, said first cladding layer and said second cladding layer being comprised of one of Group III nitrides and ternary Group III nitrides;

a first window layer formed of Mg doped GaN and disposed on said p-n junction diode heterostructure;

a second window layer formed of Mg doped GaN and disposed on said first window layer;

a conductive layer formed of NiO/Au and disposed on said second window layer, an upper surface of said conductive layer being an upper surface of the light-emitting diode;

a first opening formed at one side of the light emitting diode, and through said conductive layer such that a reflective bond pad is disposed on an upper surface of said second window layer;

a first electrode disposed on said bond pad;

a second opening formed at a central position at another side of the light emitting diode, said second opening forming a three walled notch in said light emitting diode, said second opening being formed through to said first cladding layer on which a reflective bond pad is disposed; and

a second electrode disposed on said reflective bond pad;

wherein said p-n junction diode heterostructure comprises a double heterostructure, said double heterostructure further comprising an active layer, said active layer being chosen from binary Group III nitrides, ternary Group III nitrides, quarternary Group nitrides, and alloys of SiC with such nitrides, and said first cladding layer and said second cladding layer being further chosen from quarternary Group III nitrides, and alloys of SiC with such nitrides.

5. The light-emitting diode according to claim 3, further comprising a gallium nitride epitaxial layer disposed between said buffer structure and said double heterostructure.

7. A light-emitting diode which emits light in the 400-550 nm portion of a visible spectrum, said light emitting diode comprising:

an undoped SiC substrate;

a nitride nucleating buffer structure disposed on an upper surface of said SiC substrate;

a p-n junction diode heterostructure disposed on said buffer structure, comprising;

a first cladding layer; and

a second cladding layer, said first cladding layer and said second cladding layer being comprised of one of binary Group III nitrides and ternary Group III nitrides;

a first window layer formed of Mg doped GaN and disposed on said p-n junction diode heterostructure;

a second window layer formed of Mg doped GaN and disposed on said first window layer;

a conductive layer formed of NiO/Au and disposed on said second window layer, an upper surface of said conductive layer being an upper surface of the light-emitting diode;

a first opening formed at one side of the light emitting diode, and through said conductive layer such that a reflective bond pad is disposed on an upper surface of said second window layer;

a first electrode disposed on said bond pad;

a second opening formed at a central position at another side of the light emitting diode, said second opening forming a three walled notch in said light emitting diode, said second opening being formed through to said first cladding layer on which a reflective bond pad is disposed; and

a second electrode disposed on said reflective bond pad;

wherein said p-n junction diode heterostructure comprises a double heterostructure, said double heterostructure comprising;

an active layer; and

first and second cladding layers disposed adjacent to said active layer, and formed of a composition chosen from gallium nitride, aluminum nitride, indium nitride, ternary Group III nitrides having a formula A_xB_1-xN where A and B are Group III elements and where x is one of zero, one, and a fraction between zero and one, and alloys of gallium nitride with such ternary Group III nitrides, quaternary Group III nitrides having a formula A_xB_yC_1-x-yN, where A, B, and C are Group III elements and where x is one of zero, one, and a fraction between zero and one, y is one of zero, one, and a fraction between zero and one, the sum of x and y is less than one, and alloys of gallium nitride with such quarternary Group III nitrides.

9. The light-emitting diode according to claim 7, wherein each of said first and second cladding layers adheres to a formula Al_xGa_1-xN where x is one of zero, one, and a fraction between zero and one.

10. The light-emitting diode according to claim 7, wherein each of said first and second cladding layers has a bandgap larger than said active layer.

11. The light-emitting diode according to claim 7, wherein said first cladding layer has an opposite conductivity type from said second cladding layer.

12. The light-emitting diode according to claim 7, wherein said first cladding layer is p-type and said active layer and said second cladding layer are n-type.

13. The light-emitting diode according to claim 7, wherein said first cladding layer is n-type and said active layer and said second cladding layer are p-type.

14. The light-emitting diode according to claim 7, wherein said active layer has a composition In_xGa_1-xN where x is a fraction between zero and one.

22. A light-emitting diode which emits light in a 400-550 nm portion of a visible spectrum, said light emitting diode comprising:

a lightly doped SiC substrate and having an epitaxial layer side and a light-emitting side;

a nucleating buffer structure disposed on said substrate at said epitaxial layer side;

wherein said light-emitting side of said SiC substrate is roughened;

a p-n junction diode heterostructure disposed on said buffer structure, said p-n junction diode heterostructure comprising

a first cladding layer; and

a second cladding layer, said first cladding layer and said second cladding layer being comprised of one of binary Group III nitrides, ternary Group III nitrides, and quarternary Group III nitrides;

a first window layer formed of Mg doped GaN and disposed on said p-n junction diode heterostructure;

a second window layer formed of Mg doped GaN and disposed on said first window layer;

a conductive layer formed of NiO/Au and disposed on said second window layer, an upper surface of said conductive layer being an upper surface of the light-emitting diode;

a first opening formed at one side of the light emitting diode, and through said conductive layer such that a reflective bond pad is disposed on an upper surface of said second window layer;

a first electrode disposed on said bond pad;

a second opening formed at a central position at another side of the light emitting diode, said second opening forming a three walled notch in said light emitting diode, said second opening being formed through to said first cladding layer, on which a reflective bond pad is disposed; and

a second electrode disposed on said reflective bond pad.

23. The light-emitting diode according to claim 22, wherein said buffer structure is chosen from gallium nitride, indium nitride, ternary Group III nitrides having a formula A_xB_1-xN where A and B are Group III elements and where x is one of zero, one, and a fraction between zero and one, quarternary Group III nitrides having a formula A_xB_yC_1-x-yN, where A, B, and C are Group III elements;

x and y are one of zero, one, and a fraction between zero and one, and 1 is greater than a sum of x and y, and alloys of SiC with such ternary and quarternary Group III nitrides.

25. The light-emitting diode according to claim 22, wherein said buffer structure comprises aluminum nitride.

26. The light-emitting diode according to claim 22, wherein said p-n junction diode heterostructure comprises a double heterostructure, said double heterostructure comprising:

an active layer; and

first and second cladding layers disposed adjacent to said active layer, and formed of a composition chosen from gallium nitride, aluminum nitride, indium nitride, ternary Group III nitrides having a formula A_xB_1-xN, where A and B are Group III elements and where x is one of zero, one, and a fraction between zero and one, and alloys of gallium nitride with such ternary Group III nitrides, quaternary Group III nitrides having a formula A_xB_yC_1-x-yN, where A, B, and C are Group III elements and where x is one of zero, one, and a fraction between zero and one, y is one of zero, one, and a fraction between zero and one, the sum of x and y is less than one, and alloys of gallium nitride with such quaternary Group III nitrides.

27. The light-emitting diode according to claim 22, wherein said p-n junction diode heterostructure comprises a double heterostructure, said double heterostructure comprising:

an active layer chosen from gallium nitride, aluminum nitride, indium nitride, ternary Group III nitrides having a formula A_xB_1-xN where A and B are Group III elements and where x is one of zero, one, and a fraction between zero and one, and alloys of gallium nitride with such ternary Group III nitrides, quarternary Group III nitrides having a formula A_xB_yC_1-x-yN, where A, B, and C are Group III elements and where x is one of zero, one, and a fraction between zero and one, y is one of zero, one, and a fraction between zero and one, a sum of x and y is less than one, and alloys of gallium nitride with such quaternary Group III nitrides.

28. The light-emitting diode according to claim 26, wherein each of said first and second cladding layers adheres to a formula Al_xGa_1-xN, where x is one of zero, one, and a fraction between zero and one.

24. A light-emitting diode which emits light in a 400-550 nm portion of a visible spectrum, said light emitting diode comprising:

a lightly doped SiC substrate having an epitaxial layer side and a light-emitting side;

a nucleating buffer structure disposed on said substrate at said epitaxial layer side;

wherein said light-emitting side of said SiC substrate is roughened;

a p-n junction diode heterostructure disposed on said buffer structure, said p-n junction diode heterostructure comprising

a first cladding layer; and

a second cladding layer, said first cladding layer and said second cladding layer being comprised of one of binary Group III nitrides, ternary Group III nitrides, and quaternary Group III nitrides;

a first window layer formed of Mg doped GaN and disposed on said p-n junction diode heterostructure;

a second window layer formed of Mg doped GaN and disposed on said first window layer;

a conductive layer formed of NiO/Au and disposed on said second window layer, an upper surface of said conductive layer being an upper surface of the light-emitting diode;

a first opening formed at one side of the light emitting diode, and through said conductive layer such that a reflective bond pad is disposed on an upper surface of said second window layer;

a first electrode disposed on said bond pad;

a second opening formed at a central position at another side of the light emitting diode, said second opening forming a three walled notch in said light emitting diode, said second opening being formed through to said first cladding layer, on which a reflective bond pad is disposed; and

a second electrode disposed on said reflective bond pad;

wherein said p-n junction diode heterostructure comprises a double heterostructure, said double heterostructure comprising an active layer chosen from binary Group III nitrides and ternary Group III nitrides and quarternary Group III nitrides, and alloys of SiC with such nitrides, and wherein said first cladding layer and said second cladding layer are further selected from a group consisting of alloys of SiC with such nitrides.

29. A light-emitting diode which emits light in the 400-550 nm portion of a visible spectrum, said light emitting diode comprising:

an undoped SiC substrate;

a nitride nucleating buffer structure disposed on an upper surface of said SiC substrate;

wherein a lower surface of said SiC substrate is roughened;

a light-emitting structure disposed on said buffer structure and comprising an active layer, a first cladding layer and a second cladding layer, said active layer, said first cladding layer and said second cladding layer being comprised of one of binary Group III nitrides and ternary Group III nitrides;

a first window layer formed of Mg doped GaN and disposed on said p-n junction diode heterostructure;

a second window layer formed of Mg doped GaN and disposed on said first window layer;

a conductive layer formed of NiO/Au and disposed on said second window layer, an upper surface of said conductive layer being an upper surface of the light-emitting diode;

a first opening formed at one side of the light emitting diode and through said conductive layer such that a reflective bond pad is disposed on an upper surface of said second window layer;

a first electrode disposed on said bond pad;

a second opening formed at a central position at another side of the light emitting diode, said second opening forming a three walled notch in said light emitting diode, said second opening being formed through to said first cladding layer, on which a reflective bond pad is disposed; and

a second electrode disposed on said reflective bond.

30. A light-emitting diode comprising:

an undoped SiC substrate;

a nucleating buffer structure disposed on one side of said SiC substrate;

wherein another side of said SiC substrate is roughened;

a light-emitting structure disposed on said buffer structure and comprising;

a first cladding layer;

an active layer disposed on said first cladding layer; and

a second cladding layer disposed on said active region;

a first window layer formed of Mg doped GaN and disposed on said light-emitting structure;

a second window layer formed of Mg doped GaN and disposed on said first window layer; and

a conductive layer formed of NiO/Au and disposed on said second window layer, an upper surface of said conductive layer being an upper surface of the light-emitting diode;

a first opening formed at one side of the light emitting diode and through said conductive layer such that a first reflective bond pad adhesion layer is disposed on an upper surface of said second window layer, and a first electrode is disposed on said first bond pad; and

a second opening formed at a central position at another side of the light emitting diode, said second opening forming a three walled notch in said light emitting diode, said second opening being formed through to said first cladding layer on which a second bond pad is disposed on an upper surface of said first cladding layer.

31. The light-emitting diode according to claim 30, further comprising:

a layer of undoped GaN disposed on said buffer structure, on which said light-emitting structure is disposed.

32. The light-emitting diode according to claim 30, wherein said buffer structure comprises at least one non-conducting nucleation layer.

33. The light-emitting diode according to claim 32, wherein said buffer structure is formed from GaN, AlN, InN, ternary Group III nitrides having a formula A_xB_1-xN where A and B are Group III elements and where x is one of zero, one, and a fraction between zero and one, and alloys of gallium nitride with such ternary Group III nitrides, quarternary Group III nitrides having a formula A_xB_yC_1-x-yN, where A, B, and C are Group III elements and where x is one of zero, one, and a fraction between zero and one, y is one of zero, one, and a fraction between zero and one, a sum of x and y is less than one, and alloys of SiC with such quaternary Group III nitrides.

34. The light-emitting diode according to claim 30, wherein said light-emitting structure is a double heterostructure including a p-n junction in which active and heterostructure layers are selected from the group of binary Group III nitrides, ternary Group III nitrides, quaternary Group III nitrides, and alloys of SiC with such nitrides.

35. The light-emitting diode according to claim 30, wherein said first cladding layer is formed of silicon doped GaN, said action region is formed from a silicon doped n-type GaInN/GaN MQW structure, and said second cladding layer is formed of Mg doped AlGaN.

36. The light-emitting diode according to claim 30, further comprising a first electrode disposed on said first bond pad adhesion layer.

37. The light-emitting diode according to claim 36, further comprising a second electrode disposed on said second bond pad, said second electrode being formed of Au.

38. The light-emitting diode according to claim 30, wherein each of said first and second cladding layers has a bandgap larger than said active layer.

39. The light-emitting diode according to claim 30, wherein said first cladding layer has an opposite conductivity type from said second cladding layer.

40. The light-emitting diode according to claim 30, wherein said first cladding layer is p-type and said active layer and said second cladding layer are n-type.

41. The light-emitting diode according to claim 30, wherein said first cladding layer is n-type and said active layer and said second cladding layer are p-type.