Pendeoepitaxial gallium nitride semiconductor layers on silcon carbide substrates

• US 6,177,688 B1
• Filed: 11/24/1998
• Issued: 01/23/2001
• Est. Priority Date: 11/24/1998
• Status: Expired due to Term

• Current Assignee: United States Navy (U.S. Department Of Defense)
• Original Assignee: North Carolina State University (University of North Carolina System)
• Inventors: Carlson, Eric P., Davis, Robert F., Gehrke, Thomas, Linthicum, Kevin J., Rajagopal, Pradeep, Thomson, Darren B.
• Primary Examiner(s): Munson, Gene M.
• Application Number:
  US09/198,784
• Time in Patent Office: 791 Days
• Field of Search: 257/76, 257/77, 257/190, 257/201
• US Class Current: 257/77
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H01L 21/02378 Silicon carbide
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: H01L 21/0265 Pendeoepitaxy

Abstract

An underlying gallium nitride layer on a silicon carbide substrate is masked with a mask that includes an array of openings therein, and the underlying gallium nitride layer is etched through the array of openings to define posts in the underlying gallium nitride layer and trenches therebetween. The posts each include a sidewall and a top having the mask thereon. The sidewalls of the posts are laterally grown into the trenches to thereby form a gallium nitride semiconductor layer. During this lateral growth, the mask prevents nucleation and vertical growth from the tops of the posts. Accordingly, growth proceeds laterally into the trenches, suspended from the sidewalls of the posts. The sidewalls of the posts may be laterally grown into the trenches until the laterally grown sidewalls coalesce in the trenches to thereby form a gallium nitride semiconductor layer. The lateral growth from the sidewalls of the posts may be continued so that the gallium nitride layer grows vertically through the openings in the mask and laterally overgrows onto the mask on the tops of the posts, to thereby form a gallium nitride semiconductor layer. The lateral overgrowth can be continued until the grown sidewalls coalesce on the mask to thereby form a continuous gallium nitride semiconductor layer. Microelectronic devices may be formed in the continuous gallium nitride semiconductor layer.

Claims

1. A gallium nitride semiconductor structure, comprising:

a silicon carbide substrate;

a plurality of gallium nitride posts on the silicon carbide substrate, the posts each including a sidewall and a top, and defining a plurality of trenches therebetween;

a capping layer on the tops of the posts; and

a lateral gallium nitride layer that extends laterally from the sidewalls of the posts into the trenches, wherein the posts are of a defect density and wherein the lateral gallium nitride layer is of lower defect density than the defect desity.

2. A structure according to claim 1 wherein the lateral gallium nitride layer is a continuous lateral gallium nitride layer that extends between adjacent sidewalls across the trenches therebetween.

3. A structure according to claim 1 wherein the lateral gallium nitride layer also extends vertically in the trenches, to beyond the capping layer.

4. A structure according to claim 3 further comprising a plurality of microelectronic devices in the lateral gallium nitride layer that extends vertically in the trenches, beyond the capping layer.

5. A structure according to claim 1 further comprising a plurality of microelectronic devices in the lateral gallium nitride layer.

6. A structure according to claim 1 further comprising a buffer layer between the silicon carbide substrate and the plurality of posts.

7. A structure according to claim 6 wherein the trenches extend through the buffer layer and into the silicon carbide substrate.

8. A structure according to claim 1 wherein the trenches extend into the silicon carbide substrate.

9. A structure according to claim 1 further comprising:

a microelectronic device in the lateral gallium nitride layer.

10. A structure according to claim 1 wherein the sidewall is orthogonal to the silicon carbide substrate.

11. A structure according to claim 1 wherein the sidewall is oblique to the silicon carbide substrate.

12. A structure according to claim 1 wherein the trenches include trench floors and wherein the lateral gallium nitride layer is a cantilevered lateral gallium nitride layer that extends laterally from the sidewalls of the posts into the trenches and is spaced apart from the trench floors.

13. A gallium nitride semiconductor structure, comprising:

a silicon carbide substrate;

a plurality of gallium nitride posts on the silicon carbide substrate, the posts each including a sidewall and a top, and defining a plurality of trenches therebetween;

a capping layer on the tops of the posts;

a lateral gallium nitride layer that extends laterally from the sidewalls of the posts into the trenches and that also extends vertically in the trenches, to beyond the capping layer; and

an overgrown lateral gallium nitride layer that extends laterally from the lateral gallium nitride layer onto the capping layer, wherein the posts are of a defect density and wherein the lateral gallium nitride layer and the overgrown lateral gallium nitride layer are of lower defect density than the defect density.

14. A structure according to claim 13 wherein the overgrown lateral gallium nitride layer is a continuous overgrown lateral gallium nitride layer that extends between adjacent sidewalls across the capping layer therebetween.

15. A structure according to claim 13 further comprising a plurality of microelectronic devices in the overgrown lateral gallium nitride layer.

16. A structure according to claim 13 further comprising a buffer layer between the silicon carbide substrate and the plurality of posts.

17. A structure according to claim 16 wherein the trenches extend through the buffer layer and into the silicon carbide substrate.

18. A structure according to claim 13 wherein the trenches extend into the silicon carbide substrate.

19. A structure according to claim 16 further comprising:

a microelectronic device in the overgrown lateral gallium nitride layer.

20. A structure according to claim 13 wherein the sidewall is orthogonal to the silicon carbide substrate.

21. A structure according to claim 13 wherein the sidewall is oblique to the silicon carbide substrate.

22. A structure according to claim 13 wherein the trenches include trench floors and wherein the lateral gallium nitride layer is a cantilevered lateral gallium nitride layer that extends laterally from the sidewalls of the posts into the trenches and is spaced apart from the trench floors.