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1. WO2012058535 - METHOD FOR FABRICATION OF (AL, IN, GA) NITRIDE BASED VERTICAL LIGHT EMITTING DIODES WITH ENHANCED CURRENT SPREADING OF N-TYPE ELECTRODE

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[ EN ]

WHAT IS CLAIMED IS:

1. A method of fabricating a III -nitride based optoelectronic or electronic device, comprising:

forming one or more n-type ohmic contacts to a surface of an n-type III -nitride layer in a device, wherein:

the device is Ill-nitride based,

the surface is a Ill-nitride surface,

the surface includes at least a roughened portion, and

the roughened portion is a roughened portion of a Nitrogen rich (N-rich) face of the Ill-nitride surface.

2. The method of claim 1, wherein:

the surface includes the roughened portion and at least a non-roughened (planar) portion of the N-rich face,

the n-type ohmic contacts are formed on both the roughened portion and the non-roughened portion, and

a contact resistance is lower for the n-type ohmic contacts on the roughened portion as compared to a contact resistance for the n-type ohmic contacts on the non-roughened portion.

3. The method of claim 1, wherein the roughened portion is roughened such that a current spreading in the n-type layer is increased.

4. The method of claim 1, wherein the roughened portion is roughened such that a contact resistance for the n-type ohmic contact on the roughened portion is reduced.

5. The method of claim 4, wherein the contact resistance is reduced to 1 x 10" 3 ohm centimeters squared or less.

6. The method of claim 4, wherein the contact resistance is reduced to a value less than or equal to a contact resistance for an n-type ohmic contact on a Gallium face (Ga-face) of a similar Ill-nitride layer.

7 The method of claim 1, wherein:

the device is a light emitting diode (LED), and

emission of light from the LED is uniform, with no significant increase in the emission at one or more locations for injecting drive current into the LED, for the drive current to the device of 500 milliamps or greater, or 1 amp or greater.

8. The method of claim 2, wherein the N-rich face is a semipolar plane of the Ill-nitride layer comprising at least as much nitrogen as a group III element.

9. The method of claim 8, wherein the semipolar plane is a (10-12), (11-22), or (10-11) semi-polar plane.

10. The method of claim 2, wherein the N-rich face is a Nitrogen-face of the Ill-nitride layer.

11. The method of claim 1, wherein the roughened portion is roughened by a photoelectrochemical etching or dry etching technique.

12. The method of claim 1, wherein the n-type ohmic contacts comprise metal and an annealing temperature of the n-type ohmic contacts is higher than 300 °C but lower than 600 °C.

13. The method of claim 12, wherein an annealing time, for annealing the n-type ohmic contacts, is no longer than 10 minutes.

14. The method of claim 1, wherein the device is a vertical light emitting diode.

15. The method of claim 2, wherein:

the roughened portion is an etched surface and the n-type ohmic contact on the etched surface is formed into thin metal stripes, and

the n-type ohmic contact on the non-roughened portion is a wire -bonding pad.

16. A Ill-nitride based optoelectronic or electronic device, comprising: one or more n-type ohmic contacts formed on a surface of an n-type Ill-nitride layer in a device, wherein:

the device is Ill-nitride based,

the surface is a Ill-nitride surface,

the surface includes at least a roughened portion, and

the roughened portion is a roughened portion of a Nitrogen rich (N-rich) face of the Ill-nitride surface.

17. The device of claim 16, wherein:

the surface includes the roughened portion and at least a non-roughened (planar) portion of the N-rich face,

the n-type ohmic contacts are formed on both the roughened portion and the non-roughened portion, and

a contact resistance is lower for the n-type ohmic contact on the roughened portion as compared to a contact resistance for the n-type ohmic contact on the non-roughened portion.

18. The device of claim 16, wherein the roughened portion is roughened such that a current spreading in the n-type layer is increased.

19. The device of claim 16, wherein the roughened portion is roughened such that a contact resistance for the n-type ohmic contact on the roughened portion is reduced.

20. The device of claim 19, wherein the contact resistance is reduced to 1 x 10-3 ohm centimeters squared or less.

21. The device of claim 19, wherein the contact resistance is reduced to a value less than or equal to a contact resistance for an n-type ohmic contact on a Gallium face (Ga-face) of a similar Ill-nitride layer.

22 The device of claim 16, wherein:

the device is a light emitting diode, and

emission of light from the LED is uniform, with no significant increase in the emission at one or more locations for injecting drive current into the device, for the drive current to the device of 500 milliamps or greater, or 1 amp or greater.

23. The device of claim 17, wherein the N-rich face is a semipolar plane of the Ill-nitride layer comprising at least as much nitrogen as a group III element.

24. The device of claim 23, wherein the semipolar plane is a (10-12), (11-22), or (10-11) semi-polar plane.

25. The device of claim 17, wherein the N-rich face is a Nitrogen-face of the Ill-nitride layer.

The device of claim 16, wherein the device is a vertical light emitting diode.

27. The device of claim 17, wherein:

the roughened portion is an etched surface and the n-type ohmic contact on the etched surface is formed into thin metal stripes, and

the n-type ohmic contact on the non-roughened portion is a wire -bonding pad.