Methods of fabricating gallium nitride semiconductor layers on substrates including non-gallium nitride posts

• US 6,864,160 B2
• Filed: 04/03/2002
• Issued: 03/08/2005
• Est. Priority Date: 02/09/2000
• Status: Expired due to Term

• Current Assignee: North Carolina State University (University of North Carolina System)
• Original Assignee: North Carolina State University (University of North Carolina System)
• Inventors: Davis, Robert F., Gehrke, Thomas, Linthicum, Kevin J.
• Primary Examiner(s): Mulpuri, Savitri
• Application Number:
  US10/115,354
• Publication Number:
  US 20020110997A1
• Time in Patent Office: 1,070 Days
• Field of Search: 438 22- 47, 438479-509
• US Class Current: 438/479
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/02447 Silicon carbide
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD

Abstract

A substrate includes non-gallium nitride posts that define trenches therebetween, wherein the non-gallium nitride posts include non-gallium nitride sidewalls and non-gallium nitride tops and the trenches include non-gallium floors. Gallium nitride is grown on the non-gallium nitride posts, including on the non-gallium nitride tops. Preferably, gallium nitride pyramids are grown on the non-gallium nitride tops and gallium nitride then is grown on the gallium nitride pyramids. The gallium nitride pyramids preferably are grown at a first temperature and the gallium nitride preferably is grown on the pyramids at a second temperature that is higher than the first temperature. The first temperature preferably is about 1000° C. or less and the second temperature preferably is about 1100° C. or more. However, other than temperature, the same processing conditions preferably are used for both growth steps. The grown gallium nitride on the pyramids preferably coalesces to form a continuous gallium nitride layer. Accordingly, gallium nitride may be grown without the need to form masks during the gallium nitride growth process. Moreover, the gallium nitride growth may be performed using the same processing conditions other than temperatures changes. Accordingly, uninterrupted gallium nitride growth may be performed.

Claims

1. A method of fabricating gallium nitride semiconductor structures comprising the steps of:

providing a substrate including a plurality of non-gallium nitride posts that define trenches therebetween, the non-gallium nitride posts including non-gallium nitride sidewalls and non-gallium nitride tops, and the trenches including non-gallium nitride floors; and

growing gallium nitride on the non-gallium nitride posts, including on the non-gallium nitride tops.

2. A method according to claim 1 wherein the growing step comprises the steps of:

first growing the gallium nitride at a first temperature; and

then growing the gallium nitride at a second temperature that is higher then the first temperature.

3. A method according to claim 1 wherein the following step is performed between the steps of providing and growing:

forming a conformal buffer layer on the substrate including on the non-gallium nitride sidewalls, the non-gallium nitride tops and the non-gallium nitride floors.

4. A method according to claim 1 wherein the providing step comprises the steps of:

providing a non-gallium nitride substrate; and

etching the non-gallium nitride substrate to define the plurality of non-gallium nitride posts and the trenches therebetween.

5. A method according to claim 2 wherein the first temperature is at most about 1000°

C. and wherein the second temperature is at least about 1100°

C.

6. A method according to claim 1 wherein the growing step comprises the step of masklessly growing gallium nitride on the non-gallium nitride posts, including on the non-gallium nitride taps.

7. A method according to claim 1 wherein the non-gallium nitride sidewalls expose a 11{overscore (2)}0 plane of the non-gallium nitride posts.

15. A method according to claim 1 wherein the non-gallium nitride sidewalls expose a 11{overscore (2)}0 plane of the non-gallium nitride posts.

16. A method according to claim 1, comprising growing gallium nitride on the non-gallium nitride posts in a non-vertical direction and toward the trenches.

17. A method according to claim 1, comprising growing gallium nitride on the non-gallium nitride posts in a non-vertical direction until a gallium nitride layer extends over the trenches.

18. A method according to claim 17, comprising growing gallium nitride on the non-gallium nitride posts in a non-vertical direction until gallium nitride growing on adjacent non-gallium nitride posts coalesces to form a continuous gallium nitride layer that extends over the trench defined by the adjacent non-gallium nitride posts.

19. A method according to claim 18, further comprising vertically growing the continuous gallium nitride layer.

20. A method according to claim 1, comprising growing gallium nitride on the non-gallium nitride tops of the non-gallium nitride posts in a non-vertical direction.

21. A method according to claim 1, comprising growing gallium nitride on the non-gallium nitride sidewalls of the non-gallium nitride posts in a non-vertical direction.

22. A method according to claim 1, further comprising growing gallium nitride on the non-gallium nitride floors.

23. A method according to claim 1, wherein the step of providing the substrate includes etching the substrate to form the plurality of non-gallium nitride posts that define trenches therebetween.

24. A method according to claim 1, wherein the non-gallium nitride posts are stripes.

25. A method according to claim 1, wherein the non-gallium nitride stripes extend in a 1-100 direction of the substrate.

26. A method according to claim 1, wherein the non-gallium nitride posts stripes extend in a 110 direction of the substrate.

27. A method according to claim 1, wherein the non-gallium nitride sidewalls are orthogonal to the substrate.

28. A method according to claim 1, wherein the non-gallium nitride sidewalls are oblique to the substrate.

29. A method according to claim 1, further comprising growing a gallium nitride seed form on the non-gallium nitride tops of the gallium nitride posts.

30. A method according to claim 29, comprising growing the gallium nitride seed form in a non-vertical direction.

31. A method according to claim 1, wherein the gallium nitride grown in a direction parallel to the non-gallium nitride tops has a defect density off less than or equal to about 10⁵ cm⁻

2.

32. A method according to claim 1, wherein the substrate is a silicon substrate.

33. A method according to claim 1, wherein the substrate is a sapphire substrate.

34. A method according to claim 1, wherein the substrate is a silicon carbide substrate.

35. A method according to claim 1, wherein the substrate and the non-gallium nitride posts comprise a first material.

36. A method according to claim 1, further comprising growing a conformal buffer layer on the non-gallium nitride tops of the non-gallium nitride posts prior to growing gallium nitride on the non-gallium nitride posts in a non-vertical direction.

37. A method according to claim 36, wherein the conformal buffer layer is gallium nitride.

38. A method according to claim 36, wherein the conformal buffer layer is aluminum nitride.

39. A method according to claim 1, comprising growing gallium nitride on the non-gallium nitride posts in a non-vertical direction.

40. A method according to claim 39, comprising growing gallium nitride on respective non-gallium nitride posts in a direction toward trenches formed adjacent to the respective non-gallium nitride posts.

41. A method according to claim 1, comprising laterally growing gallium nitride on non-gallium nitride posts.

8. A method of fabricating gallium nitride semiconductor structures comprising the steps of:

providing a substrate including a plurality of non-gallium nitride posts that define trenches therebetween, the non-gallium nitride posts including non-gallium nitride sidewall, and non-gallium nitride tops, and the trenches including non-gallium nitride floors;

growing gallium nitride on the substrate at a first temperature; and

then

continuing growing gallium nitride on the substrate at a second temperature that is higher than the first temperature.

9. A method according to claim 8 wherein the first temperature is at most about 1000°

C. and wherein the second temperature is at least about 1100°

C.

10. A method according to claim 8 wherein the step of continuing growing comprises the step of continuing growing gallium nitride on the substrate at the second temperature until the gallium nitride forms a continuous gallium nitride layer on the substrate.

11. A method according to claim 8 wherein the step of growing gallium nitride and the step of continuing growing gallium nitride are performed at same processing conditions other than temperature.

12. A method according to claim 8 wherein the following step is performed between the steps of providing and growing:

forming a conformal buffer layer on the substrate including on the non-gallium nitride sidewalls, the non-gallium nitride tops and the non-gallium nitride floors.

13. A method according to claim 8 wherein the providing step comprises the steps of:

providing a non-gallium nitride substrate; and

etching the non-gallium nitride substrate to define the plurality of non-gallium nitride posts and the trenches therebetween.

14. A method according to claim 8 wherein the growing and continuing growing steps comprise the steps of masklessly growing gallium nitride and masklessly continuing growing gallium nitride.