HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED) THROUGH MULTIPLE EXTRACTORS

• US 20100289043A1
• Filed: 11/15/2007
• Published: 11/18/2010
• Est. Priority Date: 11/15/2006
• 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: Murai, Akihiko, DenBaars, Steven P., Weisbuch, Claude C. A., Aurelien, David J. F.
• Application Number:
  US11/940,848
• Publication Number:
  US 20100289043A1
• Time in Patent Office: Days
• US Class Current: 257/98
• 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 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate

Abstract

An (Al,In,Ga)N and ZnO direct wafer bonded light emitting diode (LED), combined with a second light extractor acting as an additional light extraction method. This second light extraction method aims at extracting the light which has not been extracted by the ZnO structure, and more specifically the light which is trapped in the (Al,In,Ga)N layer. This second method is suited for light extraction from thin films, using surface patterning or texturing, or a photonic crystal acting as a diffraction grating. The combination of both the ZnO structure and the second light extraction method enables most of the emitted light from the LED to be extracted. In a more general extension of the present invention, the ZnO structure can be replaced by another material in order to achieve additional light extraction. In another extension, the (Al,In,Ga)N layer can be replaced by structures comprising other materials compositions, in order to achieve additional light extraction.

Claims

1. An optoelectronic device, comprising:

(a) a substrate;

(b) an active layer comprising light emitting species;

(c) a patterned mesa formed on the active layer; and

(d) an optical element grown or bonded on a top surface of the patterned mesa.

2. The device of claim 1, wherein the patterned mesa is comprised of one or more III-nitride layers.

3. The device of claim 1, wherein the patterned mesa enables light of low angle incidence to enter the optical element more efficiently, in order to obtain more optical output power.

4. The device of claim 1, wherein the optical element comprises a high refractive index material.

5. An optoelectronic device, comprising:

(a) one or more (Al,Ga,In)N layers including light emitting species;

(b) a first light extractor, comprising a shaped optical element, adjacent the (Al,Ga,In)N layers, for extracting at least a portion of the light emitted from the (Al,Ga,In)N layers; and

(c) a second light extractor, in proximity to the (Al,Ga,In)N layers and the first light extractor, for extracting additional light from the (Al,Ga,In)N layers that has not been extracted by the first light extractor.

6. The device of claim 5, wherein the first light extractor comprises a shaped structure grown on or bonded to the (Al,In,Ga)N layers.

7. The device of claim 5, wherein the second light extractor comprises a modification of either a top or bottom interface of the (Al,In,Ga)N layers or a modification within the (Al,In,Ga)N layers, and the modification comprises a pattern, a texture, or a photonic crystal.

8. The device of claim 7, wherein holes formed by the modification contain air, a dielectric, a metal, or a light-emitting material.

9. The device of claim 5, wherein the light emitting species are positioned below, within or above the second light extractor.

10. The device of claim 5, wherein the second light extractor comprises a modification of either a top or bottom interface of the first light extractor or a modification within the first light extractor, and the modification comprises a pattern, a texture, or a photonic crystal.

11. The device of claim 5, wherein the second light extractor comprises a modification of either a top or bottom interface of a substrate supporting the (Al,In,Ga)N layers or a modification within the substrate, and the modification comprises a pattern, a texture, or a photonic crystal.

12. The device of claim 5, further comprising a shaped high refractive index light extraction material for extracting even more light from the (Al,Ga,In)N layers.

13. The device of claim 5, further comprising combining or embedding the device in a light extracting structure.

14. The device of claim 13, wherein the light extracting structure contains light emitting species, which perform wavelength conversion for the light emitted by the (Al,Ga,In)N layers.

15. The device of claim 5, further comprising a substrate upon which the (Al,In,Ga)N layers reside, wherein the substrate is removed and a photonic crystal is formed on a resulting exposed surface of the (Al,In,Ga)N layers.

16. The device of claim 15, further comprising an electrical contact formed on the resulting exposed surface of the (Al,In,Ga)N layers.

17. The device of claim 16, further comprising a low index layer positioned between the resulting surface of the (Al,In,Ga)N layers and the contact, in order to diminish absorption of guided light.

18. The device of claim 17, wherein the low index layer is patterned, textured or etched with holes to diminish contact resistance between the contact and the resulting surface of the (Al,In,Ga)N layers, while maintaining low waveguide optical loss.

19. The device of claim 15, wherein the resulting surface of the (Al,In,Ga)N layers is bonded to another substrate.

20. The device of claim 5, further comprising a second optical element formed on the second light extractor.

21. A method of fabricating an optoelectronic device, comprising:

(a) providing a substrate;

(b) forming an active layer including light emitting species on the substrate;

(c) forming a patterned mesa formed on the active layer; and

(d) growing or bonding an optical element on a top surface of the patterned mesa.

22. The method of claim 21, wherein the patterned mesa is comprised of one or more III-nitride layers.

23. The method of claim 21, wherein the patterned mesa enables light of low angle incidence to enter the optical element more efficiently, in order to obtain more optical output power.

24. The method of claim 21, wherein the optical element comprises a high refractive index material.

25. A method of fabricating an optoelectronic device, comprising:

(a) forming one or more (Al,Ga,In)N layers including light emitting species;

(b) creating a first light extractor, comprising a shaped optical element adjacent the (Al,Ga,In)N layers, for extracting at least a portion of the light emitted from the (Al,Ga,In)N layers; and

(c) creating a second light extractor, in proximity to the (Al,Ga,In)N layers and the first light extractor, for extracting additional light from the (Al,Ga,In)N layers that has not been extracted by the first light extractor.