Dislocation reduction in non-polar gallium nitride thin films

• US 6,900,070 B2
• Filed: 04/15/2003
• Issued: 05/31/2005
• Est. Priority Date: 04/15/2002
• Status: Expired due to Term

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Speck, James Stephen, Craven, Michael D., Denbaars, Steven P.
• Primary Examiner(s): Fourson, George
• Assistant Examiner(s): Pham, Thanh V
• Application Number:
  US10/413,913
• Publication Number:
  US 20030230235A1
• Time in Patent Office: 777 Days
• Field of Search: 438/41, 438/46, 438/48, 438/71, 438/481, 438/584, 438/590, 438/778, 438/786, 257/E21.108, 257E21112- 3, 257/E21.117, 257E21125- 7
• US Class Current: 438/41
• CPC Class Codes: C30B 25/02 Epitaxial-layer growth
• CPC Class Codes: C30B 25/04 Pattern deposit, e.g. by using masks
• CPC Class Codes: C30B 25/105 by irradiation or electric discharge
• CPC Class Codes: C30B 25/18 characterised by the substrate
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: C30B 29/406 Gallium nitride
• CPC Class Codes: C30B 29/605 Products containing multiple oriented crystallites, e.g. columnar crystallites
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02609 Crystal orientation
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: H01L 21/02647 Lateral overgrowth

Abstract

Lateral epitaxial overgrowth of non-polar (11{overscore (2)}0) a-plane GaN seed layers reduces threading dislocations in the GaN films. First, a thin patterned dielectric mask is applied to the seed layer. Second, a selective epitaxial regrowth is performed to achieve a lateral overgrowth based on the patterned mask. Upon regrowth, the GaN films initially grow vertically through openings in the dielectric mask before laterally overgrowing the mask in directions perpendicular to the vertical growth direction. Threading dislocations are reduced in the overgrown regions by (1) the mask blocking the propagation of dislocations vertically into the growing film and (2) the bending of dislocations through the transition from vertical to lateral growth.

Claims

1. A method of reducing threading dislocation densities in a non-polar a-plane gallium nitride thin film, comprising:

(a) depositing a dielectric regrowth mask on the non-polar a-plane gallium nitride thin film;

(b) patterning the deposited mask; and

(c) performing a selective regrowth to achieve an overgrowth based on the patterned mask.

2. The method of claim 1, wherein the non-polar a-plane gallium nitride thin film comprises a seed layer.

3. The method of claim 1, wherein the depositing step comprises depositing the dielectric regrowth mask on the non-polar a-plane gallium nitride thin film via plasma-enhanced chemical vapor deposition (PECVD).

4. The method of claim 1, wherein the deposited mask is patterned with long, narrow stripe openings oriented in a variety of crystallographic directions.

5. The method of claim 1, wherein the overgrowth comprises laterally overgrown gallium nitride formed stripes.

6. The method of claim 1, wherein the performing step comprises performing a selective regrowth of the gallium nitride to achieve the overgrowth based on the patterned mask, and the gallium nitride initially grows vertically through openings in the mask before laterally overgrowing the mask in directions perpendicular to a vertical growth direction.

7. The method of claim 6, wherein laterally overgrown regions contain reduced dislocation densities, as compared to regions that grow vertically through openings in the mask.

8. The method of claim 7, wherein dislocations are reduced in the overgrown regions by the mask blocking propagation of dislocations vertically into the growing film.

9. The method of claim 7, wherein dislocations are reduced in the overgrown regions by bending of dislocations through a transition from vertical to lateral growth.

10. The method of claim 1, wherein the overgrowth is performed using a lateral epitaxial overgrowth.

11. The method of claim 1, wherein the overgrowth is performed using a method selected from a group comprising cantilever epitaxy, double lateral epitaxial overgrowth (double LEO), and SiN nanomasking.

12. A non-polar a-plane gallium nitride thin film with reduced threading dislocation densities, wherein the thin film is created using a process comprising:

(a) depositing a dielectric regrowth mask on the non-polar a-plane gallium nitride thin film;

(b) patterning the deposited mask; and

(c) performing a selective regrowth to achieve an overgrowth based on the patterned mask.

13. The thin film of claim 12, wherein the non-polar a-plane gallium nitride thin film comprises a seed layer.

14. The thin film of claim 12, wherein the depositing step comprises depositing the dielectric regrowth mask on the non-polar a-plane gallium nitride thin film via plasma-enhanced chemical vapor deposition (PECVD).

15. The thin film of claim 12, wherein the deposited mask is patterned with long, narrow stripe openings oriented in a variety of crystallographic directions.

16. The thin film of claim 12, wherein the overgrowth comprises laterally overgrown gallium nitride formed stripes.

17. The thin film of claim 12, wherein the performing step comprises performing a selective regrowth of the gallium nitride to achieve the overgrowth based on the patterned mask, and the gallium nitride initially grows vertically through openings in the mask before laterally overgrowing the mask in directions perpendicular to a vertical growth direction.

18. The thin film of claim 17, wherein laterally overgrown regions contain reduced dislocation densities, as compared to regions that grow vertically through openings in the mask.

19. The thin film of claim 18, wherein dislocations are reduced in the overgrown regions by the mask blocking propagation of dislocations vertically into the growing film.

20. The thin film of claim 18, wherein dislocations are reduced in the overgrown regions by bending of dislocations through a transition from vertical to lateral growth.

21. The thin film of claim 12, wherein the overgrowth is performed using a lateral epitaxial overgrowth.

22. The thin film of claim 12, wherein the overgrowth is performed using a method selected from a group comprising cantilever epitaxy, double lateral epitaxial overgrowth (double LEO), and SiN nanomasking.