Semiconductor device structures with modulated doping and related methods

• US 8,604,461 B2
• Filed: 12/16/2009
• Issued: 12/10/2013
• Est. Priority Date: 12/16/2009
• Status: Active Grant

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Driscoll, Daniel Carleton, Chavan, Ashonita, Saxler, Adam William
• Primary Examiner(s): HA, NATHAN W
• Application Number:
  US12/639,493
• Publication Number:
  US 20110140083A1
• Time in Patent Office: 1,455 Days
• Field of Search: 257 13- 16, 438 47- 48
• US Class Current: 257/15
• 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 21/02576 N-type
• CPC Class Codes: H01L 33/325 characterised by the doping materials

Abstract

A semiconductor device may include a doped semiconductor region having a modulated dopant concentration. The doped semiconductor region may be a silicon doped Group III nitride semiconductor region with a dopant concentration of silicon being modulated in the Group III nitride semiconductor region. In addition, a semiconductor active region may be configured to generate light responsive to an electrical signal therethrough. Related methods, devices, and structures are also discussed.

Claims

1. A semiconductor device comprising:

a doped semiconductor region wherein a dopant concentration of the semiconductor region is modulated over a plurality of intervals wherein each interval includes at least one portion having a relatively low dopant concentration and at least one portion having a relatively high dopant concentration wherein the doped semiconductor region comprises a superlattice and wherein the modulated dopant concentration is provided through at least portions of the superlattice; and

a semiconductor active region on the doped semiconductor region.

2. A semiconductor device according to claim 1 wherein the semiconductor region comprises a doped Group III nitride semiconductor region.

3. A semiconductor device according to claim 1 wherein the doped semiconductor region includes first and second adjacent intervals of modulated dopant concentration, wherein a first portion of the first interval has a first relatively low dopant concentration and a second portion of the first interval has a first relatively high dopant concentration, wherein a first portion of the second interval has a second relatively low dopant concentration and a second portion of the second interval has a second relatively high dopant concentration, wherein the first relatively high dopant concentration is greater than the first and second relatively low dopant concentrations, and wherein the second relatively low dopant concentration is less than the first and second relatively high dopant concentrations.

4. A semiconductor device according to claim 3 wherein the second portion of the first interval is between the first portions of the first and second intervals, and wherein the first portion of the second interval is between the second portions of the first and second intervals.

5. A semiconductor device according to claim 4 wherein the first and second relatively high dopant concentrations are different, and/or wherein the first and second relatively low dopant concentrations are different.

6. A semiconductor device according to claim 4 wherein the first and second relatively high dopant concentrations are the same, and/or wherein the first and second relatively low dopant concentrations are the same.

7. A semiconductor device according to claim 1 wherein the semiconductor active region comprises a multi-quantum well structure.

8. A semiconductor device according to claim 1 wherein the plurality of intervals define a repeating pattern of different dopant concentrations.

9. A semiconductor device according to claim 1 wherein the doped semiconductor region comprises a silicon doped Group III nitride semiconductor region and wherein a dopant concentration of silicon is modulated in the doped Group III nitride semiconductor region.

10. A semiconductor device according to claim 1 wherein the intervals of the modulated dopant concentration define a repeating pattern with each interval defining a period of the repeating pattern, wherein the period of the repeating pattern is greater than a period of the superlattice.

11. A semiconductor device according to claim 1 wherein the superlattice comprises a superlattice pattern of alternating layers having different concentrations of indium wherein a first of the alternating layers of the superlattice pattern has a thickness of about 5 Angstroms to about 40 Angstroms, and wherein a second of the alternating layers of the superlattice pattern has a thickness of about 5 Angstroms to about 100 Angstroms.

12. A semiconductor device according to claim 1 wherein the doped semiconductor region comprises a GaN layer and wherein the modulated dopant concentration is provided through at least portions of the GaN layer.

13. A semiconductor device according to claim 12 further comprising:

wherein the doped semiconductor region comprises a Group III nitride superlattice between the GaN layer and the active region.

14. A semiconductor device according to claim 1 wherein a relatively high dopant concentration of a respective interval is at least 50 percent greater than a relatively low dopant concentration of the respective interval.

15. A semiconductor device according to claim 14 wherein the relatively high dopant concentration of the respective interval is at least about 1.2×

1019 cm-3 and wherein the relatively low dopant concentration of the respective interval is no greater than about 6×

1018 cm-3.

16. A semiconductor device according to claim 1 further comprising:

a silicon carbide substrate on the doped semiconductor region so that the doped semiconductor region is between the silicon carbide substrate and the semiconductor active region.

17. A semiconductor device according to claim 1 wherein the doped semiconductor region comprises a doped Group III nitride semiconductor region, the semiconductor device further comprising:

a silicon carbide substrate; and

a doped AlGaN buffer layer between the silicon carbide substrate and the doped Group III nitride semiconductor region wherein the doped Group III nitride semiconductor region is between the doped AlGaN buffer layer and the semiconductor active region, and wherein a dopant concentration of the doped AlGaN buffer layer is modulated.

18. A semiconductor device according to claim 1 further comprising:

a semiconductor contact layer on the semiconductor active region so that the semiconductor active region is between the semiconductor contact layer and the doped semiconductor region, and wherein the semiconductor contact layer and the doped semiconductor region have opposite conductivity types.

19. A semiconductor device according to claim 1 wherein the doped semiconductor region comprises a doped Group III nitride semiconductor region and wherein the dopant concentration of the Group III nitride semiconductor region is modulated over the plurality of intervals to provide a sheet resistivity of less than about 30 ohms/square.

20. A semiconductor device according to claim 19 wherein the doped Group III nitride semiconductor region comprises a silicon doped GaN semiconductor layer.

21. A semiconductor device according to claim 19 wherein the Group III nitride semiconductor region is modulated to provide a sheet resistivity of less than about 20 ohms/square.

22. A semiconductor device according to claim 19 wherein the Group III nitride semiconductor region is modulated to provide a sheet resistivity of less than about 10 ohms/square.

23. A semiconductor device according to claim 11 wherein a period of the superlattice pattern includes one of the first of the alternating layers of the superlattice pattern and one of the second of the alternating layers of the superlattice pattern so that the period of the superlattice pattern is about 10 Angstroms to about 140 Angstroms.

24. A method of forming a semiconductor device, the method comprising:

forming a doped semiconductor region wherein a dopant concentration of the semiconductor region is modulated over a plurality of intervals wherein each interval includes at least one portion having a relatively low dopant concentration and at least one portion having a relatively high dopant concentration, wherein the doped semiconductor region comprises a superlattice and wherein the modulated dopant concentration is provided through at least portions of the superlattice; and

forming a semiconductor active region on the doped semiconductor region so that a current path is defined through the doped semiconductor region and the semiconductor active region.

25. A method according to claim 24 wherein the doped semiconductor region comprises a doped Group III nitride semiconductor region.

26. A method according to claim 24 wherein the doped semiconductor region includes first and second adjacent intervals of modulated dopant concentration, wherein a first portion of the first interval has a first relatively low dopant concentration and a second portion of the first interval has a first relatively high dopant concentration, wherein a first portion of the second interval has a second relatively low dopant concentration and a second portion of the second interval has a second relatively high dopant concentration, wherein the first relatively high dopant concentration is greater than the first and second relatively low dopant concentrations, and wherein the second relatively low dopant concentration is less than the first and second relatively high dopant concentrations.

27. A method according to claim 26 wherein the second portion of the first interval is between the first portions of the first and second intervals, and wherein the first portion of the second interval is between the second portions of the first and second intervals.

28. A method according to claim 27 wherein the first and second relatively high dopant concentrations are different, and/or wherein the first and second relatively low dopant concentrations are different.

29. A method according to claim 27 wherein the first and second relatively high dopant concentrations are the same, and/or wherein the first and second relatively low dopant concentrations are the same.

30. A method according to claim 24 wherein the semiconductor active region comprises a multi-quantum well structure.

31. A method according to claim 24 wherein forming a semiconductor active region precedes forming the doped semiconductor region, wherein forming the doped semiconductor region comprises forming the doped semiconductor region on the semiconductor active region.

32. A method according to claim 24 wherein the plurality of intervals define a repeating pattern of different dopant concentrations.

33. A method according to claim 24 wherein the doped semiconductor region comprises a silicon doped Group III nitride semiconductor region and wherein a dopant concentration of silicon is modulated in the Group III nitride semiconductor region.

34. A method according to claim 24 wherein the intervals of the modulated dopant concentration define a repeating pattern with each interval defining a period of the repeating pattern, wherein the period of the repeating pattern is greater than a period of the superlattice.

35. A method according to claim 24 wherein the superlattice comprises a superlattice pattern of alternating layers having different concentrations of indium wherein a first of the alternating layers of the superlattice pattern has a thickness of about 5 Angstroms to about 40 Angstroms, and wherein a second of the alternating layers of the superlattice pattern has a thickness of about 5 Angstroms to about 100 Angstroms.

36. A method according to claim 24 wherein the doped semiconductor region comprises a GaN layer and wherein the modulated dopant concentration is provided through at least portions of the GaN layer.

37. A method according to claim 36 wherein forming the doped semiconductor region precedes forming the semiconductor active region, wherein the doped semiconductor region comprises a Group III nitride superlattice between the GaN layer and the active region.

38. A method according to claim 24 wherein a relatively high dopant concentration of a respective interval is at least 50 percent greater than a relatively low dopant concentration of the respective interval.

39. A method according to claim 38 wherein the relatively high dopant concentration of the respective interval is at least about 1.2×

1019 cm-3 and wherein the relatively low dopant concentration of the respective interval is no greater than about 6×

1018 cm-3.

40. A method according to claim 24 wherein forming the doped semiconductor region comprises forming a doped Group III nitride semiconductor region on a silicon carbide substrate, wherein forming the semiconductor active region comprises forming the semiconductor active region on the doped Group III nitride semiconductor region so that the doped Group III nitride semiconductor region is between the silicon carbide substrate and the semiconductor active region.

41. A method according to claim 24 further comprising:

before forming the doped semiconductor region, forming a doped AlGaN buffer layer on a silicon carbide substrate, wherein forming the doped semiconductor region comprises forming a Group III nitride semiconductor region on the AlGaN buffer layer, and wherein a dopant concentration of the doped AlGaN buffer layer is modulated.

42. A method according to claim 24 further comprising:

forming a semiconductor contact layer on the semiconductor active region so that the semiconductor active region is between the semiconductor contact layer and the doped semiconductor region wherein the semiconductor contact layer and the doped semiconductor region have opposite conductivity types.

43. A method according to claim 35 wherein a period of the superlattice pattern includes one of the first of the alternating layers of the superlattice pattern and one of the second of the alternating layers of the superlattice pattern so that the period of the superlattice pattern is about 10 Angstroms to about 140 Angstroms.