SUPERLUMINESCENT DIODES BY CRYSTALLOGRAPHIC ETCHING

• US 20110103418A1
• Filed: 10/27/2010
• Published: 05/05/2011
• Est. Priority Date: 11/03/2009
• Status: Abandoned Application

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Kelchner, Kathryn M., Speck, James S., DenBaars, Steven P., Nakamura, Shuji, Ohta, Hiroaki, Hardy, Matthew T., Lin, You-Da
• Application Number:
  US12/913,638
• Publication Number:
  US 20110103418A1
• Time in Patent Office: Days
• US Class Current: 372/44.01
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 33/0045 the devices being superluminescent diodes
• CPC Class Codes: H01S 5/1082 with a special facet structure, e.g. structured, non planar, oblique
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

An optoelectronic device, comprising an active region and a waveguide structure to provide optical confinement of light emitted from the active region; a pair of facets on opposite ends of the device, having opposite surface polarity; and one of the facets which has been roughened by a crystallographic chemical etching process, wherein the device is a nonpolar or semipolar (Ga,In,Al,B)N based device.

Claims

1. A nonpolar or semipolar III-Nitride based optoelectronic device, comprising:

an active region;

a waveguide structure to provide optical confinement of light emitted from the active region; and

a first facet and a second facet on opposite ends of the waveguide structure, wherein the first facet and the second facet have opposite surface polarity and the first facet has a roughened surface.

2. The device of claim 1, wherein the first facet comprises a roughened c⁻

facet, c⁻

plane, or N-face of the III-Nitride device, and the second facet is a c⁺ facet, c⁺ plane, III-face, or Ga face of III-the Nitride device.

3. The device of claim 2, wherein the roughened surface is a wet etched surface.

4. The device of claim 2, wherein the roughened surface is a crystallographically etched surface.

5. The device of claim 2, wherein the roughened surface is a photoelectrochemically (PEC) etched surface.

6. The device of claim 2, wherein the roughened surface is a roughened cleaved surface, and the second facet has a cleaved surface.

7. The device of claim 2, wherein the roughened surface prevents optical feedback along an in-plane c-axis of the waveguide structure.

8. The device of claim 2, wherein the roughened surface comprises one or more structures having a diameter and height sufficiently close to a wavelength of the light that the structures scatter the light out of the waveguide.

9. The device of claim 2, wherein the roughened surface comprises one or more hexagonal pyramids having a diameter between 0.1 and 10 micrometers.

10. The device of claim 2, with an output power of at least 5 milliwatts.

11. The device of claim 2, wherein the device is a superluminescent diode (SLD).

12. The device of claim 11, wherein the roughened surface is such that an output power of the SLD increases exponentially with increasing drive current, in a linear gain regime of the SLD.

13. The device of claim 11, wherein the roughened surface is such that a full width at half maximum of the light emitted by the SLD is at least 10 times larger than without the roughening.

14. The device of claim 11, wherein the SLD emits blue light and the roughened surface is such that a full width at half maximum of the light is greater than 9 nm.

15. The device of claim 1, wherein the waveguide structure utilizes index guiding or gain guiding to reduce internal loss.

16. A method of fabricating a nonpolar or semipolar III-Nitride based optoelectronic device, comprising:

obtaining a first nonpolar or semipolar III-Nitride based optoelectronic device comprising an active region, a waveguide structure to provide optical confinement of light emitted from the active region, and a first facet and a second facet on opposite ends of the waveguide structure, wherein the first facet and the second facet have opposite surface polarity; and

roughening a surface of the first facet, thereby fabricating a second nonpolar or semipolar III-Nitride based optoelectronic device.

17. The method of claim 16, wherein the first facet comprises a roughened c⁻

plane, c⁻

facet, or N-face of the III-Nitride device, and the second facet is a c⁺ facet, c⁺ plane, Ga face or III-face of the III-Nitride device.

18. The method of claim 17, wherein the roughening is by wet etching that results in crystallographic etching.

19. The method of claim 18, wherein an etch time and concentration of the electrolyte used in the wet etching is varied to control feature size, density and total facet roughness of the first facet.

20. The method of claim 17, wherein the roughening is by a crystallographic chemical etching process.

21. The method of claim 20, wherein the crystallographic chemical etching process uses KOH at room temperature or heated.

22. The method of claim 20, wherein a photoresist developer comprising AZ 726 MIF is used during the crystallographic chemical etching process.

23. The method of claim 17, the roughening is by photoelectrochemical (PEC) etching.

24. The method of claim 17, wherein the first and second facets are formed by cleaving prior to the roughening, so that the second facet has a cleaved surface and the roughened surface is formed by roughening the first facet that has been cleaved.

25. The method of claim 17, wherein the first facet and second facet are formed by dry etching, focused ion beam (FIB) based techniques, or polishing, prior to the roughening step.

26. The method of claim 17, wherein the roughened surface prevents optical feedback along an in-plane c-axis of the waveguide structure.

27. The method of claim 17, wherein the roughened surface comprises one or more structures having a diameter and height sufficiently close to a wavelength of the light that the structures scatter the light out of the waveguide.

28. The method of claim 17, wherein the roughened surface comprises one or more hexagonal pyramids having a diameter between 0.1 and 10 micrometers.

29. The method of claim 17, with an output power of at least 5 milliwatts.

30. The method of claim 17, wherein the first device prior to the roughening step is a laser diode and the second device after the roughening step is a superluminescent diode (SLD).

31. The method of claim 30, wherein the roughened surface is such that an output power of the SLD increases exponentially with increasing drive current, in a linear gain regime of the SLD.

32. The method of claim 30, wherein the roughened surface is such that a full width at half maximum of the light emitted by the SLD is at least 10 times larger than without the roughening.

33. The method of claim 30, wherein the SLD emits blue light and the roughened surface is such that a full width at half maximum of the light is greater than 9 nm.

34. The method of claim 17, wherein the waveguide structure utilizes index guiding or gain guiding to reduce internal loss.

35. A superluminescent diode (SLDs), comprising:

a structure for a (Ga,In,Al,B)N laser diode (LD) grown on nonpolar GaN, wherein a c⁻

facet of the LD structure is crystallographically etched.