Defect reduction of non-polar and semi-polar III-nitrides with sidewall lateral epitaxial overgrowth (SLEO)

• US 20060270076A1
• Filed: 05/31/2006
• Published: 11/30/2006
• Est. Priority Date: 05/31/2005
• Status: Active Grant

• Current Assignee: Japan Science And Technology Agency
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Speck, James S., DenBaars, Steven P., Imer, Bilge M.
• Granted Patent: US 7,361,576 B2
• Time in Patent Office: Days
• US Class Current: 438/22
• 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 21/02516 Crystal orientation
• 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
• CPC Class Codes: H01L 21/0265 Pendeoepitaxy

Abstract

A method of reducing threading dislocation densities in non-polar such as a-{11-20} plane and m-{1-100} plane or semi-polar such as {10-1n} plane III-Nitrides by employing lateral epitaxial overgrowth from sidewalls of etched template material through a patterned mask. The method includes depositing a patterned mask on a template material such as a non-polar or semi polar GaN template, etching the template material down to various depths through openings in the mask, and growing non-polar or semi-polar III-Nitride by coalescing laterally from the tops of the sidewalls before the vertically growing material from the trench bottoms reaches the tops of the sidewalls. The coalesced features grow through the openings of the mask, and grow laterally over the dielectric mask until a fully coalesced continuous film is achieved.

Claims

1. A method of reducing threading dislocation densities in non-polar and semi-polar III-Nitride material, comprising:

(a) performing a lateral epitaxial overgrowth of non-polar or semi-polar III-Nitride material from sidewalls of etched template material through a patterned mask.

2. The method of claim 1, wherein the material is any non-polar or semi-polar crystal orientation of III-Nitride material.

3. The method of claim 1, further comprising:

(1) forming the patterned mask on the template material;

(2) etching the template material through one or more openings in the patterned mask to form one or more trenches or pillars in the template material, wherein the trenches or pillars define the sidewalls; and

(3) growing the non-polar or semi-polar III-Nitride material laterally from tops of the sidewalls and vertically from bottoms of the trenches, wherein the III-Nitride material growing laterally from the tops of the sidewalls coalesces before the III-Nitride material growing vertically from the bottoms of the trenches reaches the tops of the sidewalls.

4. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material growing laterally from the tops of the sidewalls blocks the non-polar or semi-polar III-Nitride material growing vertically from the bottoms of the trenches.

5. The method of claim 3, wherein the openings are aligned to create planar sidewalls in subsequent lateral growth steps.

6. The method of claim 3, wherein the template material has a thickness comparable or scaled relative to the openings'"'"' dimensions to compensate for competing lateral to vertical growth rates.

7. The method of claim 6, wherein the etching is performed to one or more etch depths comparable or scaled to the openings'"'"' dimensions in order for the non-polar or semi-polar III-Nitride material growing from the tops of the sidewalls to coalesce before the non-polar or semi-polar III-Nitride material growing from the bottoms of the trenches reaches the tops of the sidewalls.

8. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material grows vertically up through the openings after coalescence.

9. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material grows through the openings after coalescence, and then grows laterally over the patterned mask to form an overgrown non-polar or semi-polar III-Nitride film.

10. The method of claim 9, wherein dislocation densities are reduced by eliminating or reducing defects in the overgrown non-polar or semi-polar III-Nitride material.

11. The method of claim 3, further comprising reducing dislocation densities at least one order of magnitude lower than that achieved in III-Nitride materials using conventional single step lateral epitaxial overgrowth.

12. The method of claim 3, wherein:

to control a lateral and vertical growth rate, growth conditions for a-{11-20} plane gallium nitride (GaN) films are specified by;

a temperature in a range of 1000-1250°

C., a reactor pressure in a range of 20-760 Torr, and a V/III ratio in a range of 100-3500 at different stages of the growth, wherein the growth conditions are such that the lateral growth rate is greater than the vertical growth rate.

13. The method of claim 3, wherein the non-polar or semi-polar III-Nitride material grows only from regions of exposed template material, but not on the patterned mask.

14. The method of claim 3;

further comprising;

decreasing stacking fault densities with an anisotropy factor, by encouraging higher growth rates on a gallium (Ga) face of the non-polar III-Nitride material and limiting growth rates on a nitrogen (N) face of the non-polar III-Nitride material, thereby reducing stacking fault densities at least one order of magnitude lower than that achieved in Nitride material using conventional single step lateral epitaxial overgrowth, and confining stacking faults to N faces.

15. The method of claim 3, further comprising:

preventing growth from the bottoms of the trenches by etching to a substrate or depositing an additional mask on the bottoms of the trenches.

16. A device, wafer, substrate or template manufactured using the method of claim 1.

17. A method of reducing threading dislocation densities in epitaxially grown non-polar or semi-polar III-Nitride films, devices or substrates, comprising:

(a) performing a lateral epitaxial overgrowth of epitaxial material from sidewalls of etched template material through a patterned mask, comprising;

(1) forming the patterned mask on the template material;

(2) etching the template material through one or more openings in the patterned mask to form one or more trenches or pillars in the template material, the one or more trenches or pillars comprising the sidewalls, tops of the sidewalls and one or more bottoms; and

(3) growing and coalescing the epitaxial material laterally from the tops before epitaxial material vertically growing from the one or more bottoms reaches the tops;

(4) growing the epitaxial material vertically up through the one or more openings after the growing and coalescing step (3);

(5) growing the epitaxial material laterally over the patterned mask to form overgrown material which may form a continuous film, after the growing and coalescing step (3),

wherein the growth in steps (3) and (5) is performed using a lateral overgrowth technique.