HIGH LIGHT EXTRACTION EFFICIENCY NITRIDE BASED LIGHT EMITTING DIODE BY SURFACE ROUGHENING

• US 20090146170A1
• Filed: 12/01/2008
• Published: 06/11/2009
• Est. Priority Date: 11/30/2007
• 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: Vampola, Kenneth J., Speck, James S., Tyagi, Anurag, DenBaars, Steven P., Nakamura, Shuji, Zhong, Hong
• Granted Patent: US 8,114,698 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 33/0075 comprising nitride compounds
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/18 within the light emitting region
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A III-nitride light emitting diode (LED) and method of fabricating the same, wherein at least one surface of a semipolar or nonpolar plane of a III-nitride layer of the LED is textured, thereby forming a textured surface in order to increase light extraction. The texturing may be performed by plasma assisted chemical etching, photolithography followed by etching, or nano-imprinting followed by etching.

Claims

1. A method for fabricating a III-nitride light emitting diode (LED), comprising:

texturing at least one surface of a semipolar or nonpolar plane of a III-nitride layer of the LED to form a textured surface, wherein the texturing step is performed by plasma assisted chemical etching.

2. The method of claim 1, wherein the texturing step is performed by photolithography followed by the etching.

3. The method of claim 1, wherein the textured surface is formed using nano-imprinting followed by the etching.

4. The method of claim 1, wherein light emitted by an active region of the LED is extracted from the textured surface.

5. The method of claim 1, wherein the texturing step further comprises:

(1) creating at least one feature with at least one sidewall that reflects and transmits at least one light ray incident from inside the feature; and

(2) inclining the sidewall such that each time the ray is reflected, an angle of incidence of the ray relative to a surface normal of the sidewall decreases, such that;

(a) when the angle of incidence of the ray is smaller than a critical angle, the ray'"'"'s transmission through the sidewall is increased, and

(b) when the angle of incidence of the ray is at least equal to the critical angle, the ray is reflected by the sidewall.

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

emitting the light from at least one textured surface of a semipolar or nonpolar plane of a III-nitride layer of the LED, wherein the texturing is performed by plasma assisted chemical etching.

7. A III-nitride light emitting diode (LED), comprising:

(a) n-type III-nitride;

(b) p-type III-nitride;

(c) a III-nitride active layer, that emits light, formed between the n-type III-nitride and p-type III-nitride;

(d) a III-nitride light extraction surface on the n-type III-nitride and forming an interface with an external medium, wherein the III-nitride light extraction surface has features with at least one sloped sidewall which transmits the light into external medium air at the interface and reflects the light at the interface, wherein;

(1) the reflected light, after undergoing subsequent reflections inside the features, has an increased incidence angle relative to the interface and consequently an increased chance of being transmitted to the external medium, and

(2) the n-type III-nitride, p-type III-nitride, and III-nitride active layer are semi-polar or non-polar layers.

8. The LED of claim 7, wherein the external medium is a medium with a smaller refractive index than III-nitride.

9. The LED of claim 7, wherein the external medium is air or a vacuum.