In-situ defect reduction techniques for nonpolar and semipolar (Al, Ga, In)N

• US 7,723,216 B2
• Filed: 05/09/2007
• Issued: 05/25/2010
• Est. Priority Date: 05/09/2006
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Chakraborty, Arpan, Kim, Kwang-Choong, Speck, James S., DenBaars, Steven P., Mishra, Umesh K.
• Primary Examiner(s): Toledo; Fernando L
• Assistant Examiner(s): DIALLO, MAMADOU L
• Application Number:
  US11/801,283
• Publication Number:
  US 20070267654A1
• Time in Patent Office: 1,112 Days
• Field of Search: 438/689, 438/483, 257/79, 257/190
• US Class Current: 438/483
• 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 21/02516 Crystal orientation
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02639 Preparation of substrate for selective deposition
• CPC Class Codes: H01L 33/007 comprising nitride compounds

Abstract

A method for growing reduced defect density planar gallium nitride (GaN) films is disclosed. The method includes the steps of (a) growing at least one silicon nitride (SiN_x) nanomask layer over a GaN template, and (b) growing a thickness of a GaN film on top of the SiN_x nanomask layer.

Claims

1. A method for growing a reduced defect density nonpolar or semipolar III-nitride layer, comprising:

(a) growing at least one nonpolar or semipolar III-nitride layer on top of at least one SiN_x nanomask layer, which results in the nonpolar or semipolar III-nitride layer having a planar top surface that is a nonpolar or semipolar plane and a reduced defect density as compared to a nonpolar or semipolar III-nitride layer grown without the SiN_x nanomask layer.

2. The method of claim 1, wherein the nonpolar or semipolar III-nitride layer is a planar, coalesced film.

3. The method of claim 1, wherein the nonpolar or semipolar III-nitride layer is GaN.

4. The method of claim 1, wherein the growth of the nonpolar or semipolar III-nitride layer on top of the SiN_x nanomask layer is a nano lateral epitaxial overgrowth on at least one open pore in the SiN_x nanomask layer, with the nonpolar or semipolar III-nitride layer growing through the open pore and laterally over the SiN_x nanomask layer.

5. The method of claim 4, wherein the open pore is a nanoscale open pore.

6. The method of claim 1, further comprising growing the SiN_x nanomask layer over a III-nitride template prior to growing the nonpolar or semipolar III-nitride layer.

7. The method of claim 6, wherein the growth of the SiN_x nanomask layer is in-situ with the growth of the nonpolar or semipolar III-nitride layer.

8. The method of claim 6, wherein the III-nitride template comprises a growth on a substrate of a nitride nucleation layer followed by approximately 0.5 μ

m thick III-nitride layer to achieve coalescence below the SiN_x layer.

9. The method of claim 6, wherein the III-nitride template is a nonpolar or semipolar template.

10. The method of claim 6, wherein the III-nitride template is a free-standing wafer.

11. The method of claim 6, wherein the growth of the SiN_x nanomask layer is in a nitrogen ambient and at a high growth temperature of approximately 1000-1200°

C. to achieve a high growth rate for the SiN_x nanomask layer.

12. The method of claim 6, wherein the SiN_x nanomask layer is grown to a specified thickness achieved by flowing disilane and ammonia in nitrogen ambient for a specified period of time.

13. The method of claim 6, wherein the growth of the SiN_x nanomask layer is in a nitrogen ambient and at a high pressure of approximately 500-760 Torr to achieve a high growth rate for the SiN_x nanomask layer.

14. The method of claim 6, wherein the growth of the SiN_x nanomask layer is in a nitrogen ambient and at a low ammonia partial pressure of approximately 1 slpm of ammonia in a total mixture of approximately 10 slpm to achieve a high growth rate for the SiN_x nanomask layer.

15. The method of claim 1, wherein a thicker SiN_x nanomask layer leads to lower defect density for the nonpolar or semipolar III-nitride layer.

16. The method of claim 1, wherein an optimum SiN_x nanomask layer thickness is approximately 0.4-1 nm.

17. The method of claim 1, wherein the nonpolar or semipolar III-nitride layer does not form a coalesced film for the SiN_x nanomask layer having a thickness greater than 1.5 nm.

18. The method of claim 1, wherein the SiN_x nanomask layer is comprised of a growth of SiN_x islands.

19. The method of claim 1, wherein the nonpolar or semipolar III-nitride layer is grown on the SiN_x nanomask layer at an intermediate growth temperature of approximately 800-1000°

C. to help in further reduction of defect density by increasing three-dimensional island size in the nonpolar or semipolar III-nitride layer.

20. A device fabricated using the method of claim 1.

21. A device, comprising:

(a) at least one SiN_x nanomask grown on a III-nitride template; and

(b) nonpolar or semipolar III-nitride grown on top of the SiN_x nanomask and having a planar top surface that is a nonpolar or semipolar plane and having a reduced defect density as compared to nonpolar or semipolar III-nitride grown without the SiN_x nanomask.

22. The device of claim 21, wherein the nonpolar or semipolar III-nitride is GaN.

23. The device of claim 21, wherein the nonpolar or semipolar III-nitride has a threading dislocation density less than 9×

10⁹ cm<sup>−

2</sup> and a stacking fault density less than 3×

10⁵ cm<sup>−

1</sup>.

24. The device of claim 21, wherein the nonpolar or semipolar III-nitride is characterized by

on-axis X-Ray Rocking Curve (XRC) Full Width at Half Maximums (FWHM) less than 0.29°

(1040″

) and 0.25°

(924″

) for φ

=0° and

φ

=90°

, respectively; and

off-axis XRC FWHMs less than 0.42°

(1508″

), 0.38°

(1375″

) and 0.33°

(1208″

) for (101), (201) and (102) reflections, respectively.

25. The device of claim 21, wherein the nonpolar or semipolar III-nitride has a surface roughness of at most 0.6 nm in a 5 μ

m×

5 μ

m area.

26. The device of claim 21, wherein the nonpolar or semipolar III-nitride is a film having an optimum thickness of approximately 1 μ

m or thicker.

27. The device of claim 21, wherein the nonpolar or semipolar III-nitride is a film having an electron mobility of at least 167 cm²/Vs.