METHOD FOR GROWTH OF SEMIPOLAR (Al,In,Ga,B)N OPTOELECTRONIC DEVICES

• US 20070252164A1
• Filed: 02/20/2007
• Published: 11/01/2007
• Est. Priority Date: 02/17/2006
• 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: Sharma, Rajat, Nakamura, Shuji, Zhong, Hong, DenBaars, Steven, Kaeding, John, Speck, James
• Granted Patent: US 7,858,996 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: C30B 25/186 being specially pre-treated by, e.g. chemical or physical means
• CPC Class Codes: C30B 29/403 AIII-nitrides
• CPC Class Codes: H01L 21/02389 Nitrides
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/02647 Lateral overgrowth
• CPC Class Codes: H01L 21/02658 Pretreatments cleaning in general H01L21/02041
• CPC Class Codes: H01L 29/2003 Nitride compounds
• CPC Class Codes: H01L 29/778 with two-dimensional charge carrier gas channel, e.g. HEMT ; with two-dimensional charge-carrier layer formed at a heterojunction interface H01L29/803 takes precedence
• CPC Class Codes: H01L 31/0236 Special surface textures
• CPC Class Codes: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy

Abstract

A method of fabricating an optoelectronic device, comprising growing an active layer of the device on an oblique surface of a suitable material, wherein the oblique surface comprises a facetted surface. The present invention also discloses a method of fabricating the facetted surfaces. One fabrication process comprises growing an epitaxial layer on a suitable material, etching the epitaxial layer through a mask to form the facets having a specific crystal orientation, and depositing one or more active layers on the facets. Another method comprises growing a layer of material using a lateral overgrowth technique to produce a facetted surface, and depositing one or more active layers on the facetted surfaces. The facetted surfaces are typically semipolar planes.

Claims

1. A device, comprising:

(a) one or more oblique or facetted surfaces of a substrate or template.

2. The device of claim 1, wherein the oblique or facetted surfaces are semipolar or nonpolar planes.

3. The device of claim 1, wherein the oblique or facetted surfaces comprise {1122}, {1011}, {1013}, {1012}, {2021}, or {1014} planes.

4. The device of claim 1, wherein the oblique or facetted surfaces are formed on a surface of the substrate or template and the substrate or template is c-plane before the oblique or facetted surfaces are formed.

5. The device of claim 1, wherein the oblique or facetted surfaces are etched oblique or facetted surfaces of the substrate or template.

6. The device of claim 1, wherein the oblique or facetted surfaces are sidewalls or facets of trenches, grooves, or pits in a surface of the template or substrate.

7. The device of claim 6, wherein the trenches, grooves, or pits have a maximum depth not greater than 10 microns and a spacing in a range between 3 and 10 microns.

8. The device of claim 1, wherein the oblique or facetted surfaces are surfaces of epitaxial lateral overgrowths of the substrate or template.

9. The device of claim 1, further comprising:

(b) one or more active layers formed epitaxially on the oblique or facetted surfaces or on one or more epitaxial layers formed on the oblique or facetted surfaces.

10. The device of claim 9, wherein the active layers or epitaxial layers are homoepitaxial or regrowths.

11. The device of claim 9, wherein the device is a substrate, light emitting diode (LED), laser diode (LD), an electrically injected device, other device where the active layers are light emitting, a high electron mobility transistor, or a device which would benefit from a reduction in internal polarization fields or increased hole mobility.

12. The device of claim 9, further comprising:

(c) one or more n-type nitride layers; and

(d) one or more p-type nitride layers, (e) wherein the active layers are light emitting and nitride based, and positioned between the n-type nitride layers and the p-type nitride layers.

13. The device of claim 9, further comprising:

(c) an n-type waveguide layer;

(d) a p-type waveguide layer;

(e) one or more n-type layers above or below the n-type waveguide layer; and

(f) one or more p-type layers above or below the n-type waveguide layers. (g) wherein the active layers are light emitting and positioned between the n type waveguide layer and the p-type waveguide layer.

14. The device of claim 9, wherein at least one of the active layers, substrate, template, or epitaxial layers comprise (Al, Ga, In, B)N-based material or is suitable for growth of (Al, Ga, In, B)N material.

15. The device of claim 9, wherein the active layers are comprised of multi quantum well (MQW) layers comprising indium.

16. The device of claim 9, wherein the epitaxial layers or template, or both the epitaxial layers and template, comprise n-type or p-type material.

17. The device of claim 9, further comprising one or more n-type or p-type layers above the active layers.

18. A method for fabricating a semiconductor device having one or more crystallographic orientations, comprising:

(a) forming one or more oblique surfaces or inclined facets of a substrate or template.

19. The method of claim 18, wherein the oblique surfaces or inclined facets are formed with a semipolar or nonpolar orientation.

20. The method of claim 18, wherein the template comprises (Al,Ga,In,B)N material or is suitable for growth of nitride material, or the substrate is bulk aluminium nitride or gallium nitride, or both the substrate and template comprise (Al,Ga,In,B)N material or are suitable for growth of (Al, Ga, In, B)N material.

21. The method of claim 18, wherein the template or substrate is c-plane.

22. The method of claim 18, wherein the template comprises at least one of the following:

one or more laterally epitaxially overgrown layers for defect reduction, one or more n-doped or p-doped layers of a device, or one or more layers with varying refractive index to form a distributed Bragg reflector.

23. The method of claim 18, wherein the forming comprises etching the template or substrate.

24. The method of claim 23, wherein the etching is dry etching and a greater inclination for the oblique surfaces or inclined facets is achieved by a greater degree of chemical etching and a lesser degree of physical etching.

25. The method of claim 23, wherein the etching comprises etching one or more areas of a surface of the substrate or template to form pits, trenches or grooves having sidewalls which are the oblique surfaces or inclined facets.

26. The method of claim 23, wherein:

(1) the etching comprises etching one or more areas of a surface of the substrate or template to a maximum depth in a range between 1 nanometer and 10 microns which determines a surface area of the oblique surfaces; and

(2) the areas have a width in a range between 3 and 10 microns which determines an angle of inclination of the oblique surfaces or inclined surfaces.

27. The method of claim 23, wherein the etching further comprises:

(1) masking areas on the substrate or template, to create masked and unmasked areas; and

(2) etching the substrate or template through the unmasked areas, wherein the masked areas are etched at a relatively slower rate than the unmasked areas.

28. The method of claim 27, wherein the masked and unmasked areas are formed using nanoimprinting.

29. The method of claim 27, wherein the masked areas are stripes having a spacing that determines an inclination angle of the oblique surfaces or inclined facets.

30. The method of claim 29, wherein the spacing ranges between 3 and 10 microns.

31. The method of claim 18, wherein the forming step further comprises:

(1) performing an epitaxial lateral overgrowth of the substrate or template, wherein the epitaxial lateral overgrowth comprises lateral epitaxial overgrowth (LEO), side-wall epitaxial lateral overgrowth (SELO), or cantilevered epitaxial lateral overgrowth (CELO); and

(2) terminating the epitaxial lateral overgrowth before adjacent overgrowth stripes coalesce, wherein one or more surfaces of the epitaxial overgrowth comprise the oblique surfaces or inclined facets.

32. The method of claim 18, wherein the oblique surfaces or inclined facets do not all have a same orientation.

33. The method of claim 18, wherein the oblique surfaces or inclined facets are formed with an inclination angle in the range 25 to 50 degrees.

34. The method of claim 18, further comprising annealing the oblique surfaces or inclined facets after the forming step (a) to create crystallographic facets with semipolar orientation.

35. The method of claim 18, further comprising:

(b) depositing one or more epitaxial layers on the oblique surfaces or inclined facets formed in step (a).

36. The method of claim 35, wherein the oblique surfaces or inclined facets are formed with an inclination angle larger than is desired because the depositing step (b) reduces the inclination angle to the desired inclination angle.

37. The method of claim 35, wherein metalorganic chemical vapor deposition, molecular beam epitaxy, sublimation, vapor phase epitaxy, or ammonothermal growth are used to deposit the epitaxial layers.

38. The method of claim 35, wherein at least the first epitaxial layer is regrown or homoepitaxially deposited.

39. The method of claim 35, wherein the epitaxial layers comprise at least one of the following:

one or more n-type layers, one or more p-type layers, or one or more (Al,In,Ga,B)N layers.

40. The method of claim 35, wherein the depositing step (b) further comprises:

(1) regrowing an n-type gallium nitride (GaN) layer on the oblique surfaces or inclined facets using metalorganic chemical vapor deposition (MOCVD), at a raised wafer temperature of approximately 1050°

C., under a flow of hydrogen, nitrogen and ammonia;

(2) lowering the wafer temperature to approximately 800°

C. and depositing one or more light emitting (In,Ga)N layers on the regrown n-type GaN layer; and

(3) depositing one or more further device layers on the light emitting (In,Ga)N layers.

41. The method of claim 35, wherein the depositing step (b) results in a final surface which is substantially planar.

42. A device fabricated using the method of claim 18.

43. The device of claim 42, wherein the device is a substrate, light emitting diode, a laser diode, a photovoltaic cell, a high electron mobility transistor, or a device which would benefit from a reduction in internal polarization fields or increased hole mobility.