ENHANCEMENT OF OPTICAL POLARIZATION OF NITRIDE LIGHT-EMITTING DIODES BY WAFER OFF-AXIS CUT

• US 20100052008A1
• Filed: 02/02/2009
• Published: 03/04/2010
• Est. Priority Date: 02/01/2008
• 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: Saito, Makoto, Speck, James S., DenBaars, Steven P., Nakamura, Shuji, Masui, Hisashi, Yamada, Hisashi, Iso, Kenji, Hirai, Asako
• Granted Patent: US 8,278,128 B2
• Time in Patent Office: Days
• US Class Current: 257/103
• CPC Class Codes: H01L 33/16 with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

An off-axis cut of a nonpolar III-nitride wafer towards a polar (−c) orientation results in higher polarization ratios for light emission than wafers without such off-axis cuts. A 5° angle for an off-axis cut has been confirmed to provide the highest polarization ratio (0.9) than any other examined angles for off-axis cuts between 0 and 27°.

Claims

1. A method for increasing a polarization ratio of light emission from a light-emitting diode (LED), comprising:

performing an off-axis cut of a nonpolar III-nitride towards a polar (−

c or +c) orientation; and

growing the LED on the off-axis cut of the nonpolar III-nitride, thereby increasing the polarization ratio of light emission from the LED.

2. The method of claim 1, wherein the light emission has a higher polarization ratio than without the off-axis cut.

3. The method of claim 1, wherein the off-axis cut has an off-axis cut angle between 0°

and 27° and

the orientation is [000-1].

4. The method of claim 1, wherein the off-axis cut angle is about 5°

to provide a higher polarization ratio than other off-axis cut angles between 0° and

27°

.

5. The method of claim 1, wherein the polarization ratio for an off-axis cut angle of 5°

at the light emission'"'"'s wavelength of 450 nm is about 0.91.

6. The method of claim 1, wherein the polarization ratio for an off-axis cut angle of 10°

at the light emission'"'"'s wavelength of 430 nm exceeds 0.80.

7. The method of claim 1, wherein the polarization ratio for an off-axis cut angle of 0°

at the light emission'"'"'s wavelength of 470 nm exceeds 0.80.

8. The method of claim 1, wherein the polarization ratio for an off-axis cut angle of 27°

at the light emission'"'"'s wavelength of 450 nm is about 0.55.

9. The method of claim 1, wherein the polarization ratio for an off-axis cut angle of 0°

at the light emission'"'"'s wavelength of 390 nm is about 0.55.

10. The method of claim 1, wherein the LED is a nonpolar LED.

11. A light-emitting diode (LED) fabricated according to the method of claim 1.

12. A light-emitting diode (LED), comprising:

one or more light-emitting layers on a surface of a nonpolar oriented III-nitride, wherein;

the surface is at an off-axis angle with respect to a nonpolar plane of the nonpolar oriented III-nitride,

the angle is towards a [0001] or [000-1] direction or orientation of the nonpolar oriented III-nitride, and

the angle achieves a polarization ratio for light emitted by the light-emitting layers in excess of 0.8.

13. A method for emitting light from a light-emitting diode (LED), comprising:

emitting the light from one or more light-emitting layers on a surface of a nonpolar oriented III-nitride, wherein;

the surface is at an off-axis angle with respect to a nonpolar plane of the nonpolar oriented III-nitride,

the angle is towards a [0001] or [000-1] direction or orientation, and

the angle achieves a polarization ratio for the light emitted from the light-emitting layers in excess of 0.8.