Nano-air-bridged lateral overgrowth of GaN semiconductor layer

• US 20060270201A1
• Filed: 05/15/2006
• Published: 11/30/2006
• Est. Priority Date: 05/13/2005
• Status: Abandoned Application

• Current Assignee: National University of Singapore
• Original Assignee: National University of Singapore
• Inventors: Chua, Soo Jin, Wang, Yadong, Zang, Keyan
• Application Number:
  US11/434,399
• Publication Number:
  US 20060270201A1
• Time in Patent Office: Days
• US Class Current: 438/481
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/183 being provided with a buffer layer, e.g. a lattice matching layer
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/0243 Surface structure
• 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

A technique for growing a high quality gallium nitride layer on a uniform nano-patterned substrate is described. The invented technique is based on the transfer of ordered nano-patterns from a nano-template to the substrate, followed by the growth of gallium nitride on the nano-patterned substrate. The nano-patterned substrate serves as a buffer layer to reduce the stress and dislocations.

Claims

1. A method of growing a high-quality Group-III nitride layer on a substrate comprising the following steps:

(i) depositing a Group-III nitride layer on said substrate;

(ii) forming a nano-template having an array of defined nano-channels extending through to underlying said Group-III nitride layer;

(iii) etching underlying said Group-III nitride layer and forming nano-pores in said Group-III nitride layer and nano-posts between said nano-pores, using said nano-template as an etching mask, wherein said nano-posts and nano-pores form a nano-patterned Group-III nitride surface;

(iv) removing said nano-template; and

(v) growing said high-quality Group-III nitride layer on said nano-posts and air-bridging over said nano-pores to achieve lateral coalescence and hence to form a continuous high-quality Group-III nitride layer overlying said nano-posts and said nano-pores.

2. The method according to claim 1 wherein said substrate comprises a material that can be used in Group-III nitride growth.

3. The method according to claim 1 wherein said nano-template comprises any material having nano-patterns in it.

4. The method according to claim 1 wherein forming said nano-template comprises forming a nanoporous anodic aluminum oxide thin film on said Group-III nitride layer on said substrate.

5. The method according to claim 1 wherein forming said nano-template comprises:

forming a metal film on said group-III nitride layer on said substrate; and

anodizing said metal film into an anodic metal oxide layer having said nano-channels therethrough.

6. The method according to claim 1 wherein said etching step comprises:

dry etching, wet etching or any other etching process.

7. The method according to claim 1 wherein said nano-patterned Group-III nitride surface has nano-patterns comprising any shape with geometrical scale up to hundreds of nanometers.

8. The method according to claim 1 wherein said growing said high-quality Group-III nitride layer comprises growth on top of said nano-posts and air-bridge-mediated lateral overgrowth.

9. The method according to claim 8 wherein growth is inhibited inside said nano-pores.

10. The method according to claim 8 wherein a rate of said lateral overgrowth is controlled by growth conditions, temperature, pressure, and reactant flow rates.

11. The method according to claim 1 further comprising:

growing a subsequent Group III-nitride epilayer overlying said high-quality Group-III nitride layer.

12. The method according to claim 1 said high quality Group-III nitride layer has increased stress relaxation and reduced dislocation density as compared to first said Group-III nitride layer.

13. A method of growing a high-quality gallium nitride layer on a nano-patterned gallium nitride surface of a substrate comprising the following steps:

(i) depositing a gallium nitride layer on said substrate;

(ii) forming a nano-template having an array of defined nano-channels extending through to underlying said gallium nitride layer;

(iii) etching underlying said gallium nitride layer and forming nano-pores in said gallium nitride layer and nano-posts between said nano-pores, using said nano-template as an etching mask, wherein said nano-posts and nano-pores form said nano-patterned gallium nitride surface;

(iv) removing said nano-template; and

(v) growing said high-quality gallium nitride layer on said nano-posts and air- bridging said nano-pores to achieve lateral coalescence and hence to form a continuous high-quality gallium nitride layer overlying said nano-posts and said nano-pores.

14. The method according to claim 13 wherein said substrate comprises a material that can be used in gallium nitride growth.

15. The method according to claim 13 further comprising a buffer layer between said substrate and said gallium nitride layer.

16. The method according to claim 13 wherein said nano-template comprises any material with nano-patterns in it.

17. The method according to claim 13 wherein forming said nano-template comprises forming a nanoporous anodic aluminum oxide thin film on said gallium nitride layer on said substrate.

18. The method according to claim 17 wherein forming said nano-template further comprises:

forming a metal film on said gallium nitride layer on said substrate; and

anodizing said metal film into an anodic metal oxide layer.

19. The method according to claim 13 wherein said etching step comprises:

dry etching, wet etching or any other etching process.

20. The method according to claim 13 wherein said nano-patterned gallium nitride surface has nano-patterns comprising any shape with geometrical scale up to hundreds of nanometers.

21. The method according to claim 13 wherein said growing said high-quality gallium nitride layer comprises growth on top of said nano-posts and air-bridge-mediated lateral overgrowth.

22. The method according to claim 21 wherein growth is inhibited inside said nano-pores.

23. The method according to claim 21 wherein a rate of said lateral overgrowth is controlled by growth conditions, temperature, pressure, and reactant flow rates.

24. The method according to claim 13 further comprising:

growing an additional gallium nitride layer on top of said high-quality gallium nitride layer.

25. The method according to claim 13 further comprising:

growing a subsequent Group III-nitride epilayer overlying said high-quality gallium nitride layer.

26. A high-quality Group-III nitride layer on a substrate comprising:

a Group-III nitride layer on said substrate;

a nano-pattern of nano-pores in said Group-III nitride layer having nano-posts therebetween; and

said high-quality Group-III nitride layer overlying said nano-posts and said nano- pores.