HIGH LIGHT EXTRACTION EFFICIENCY LIGHT EMITTING DIODE (LED) WITH EMITTERS WITHIN STRUCTURED MATERIALS

• US 20080135864A1
• Filed: 11/15/2007
• Published: 06/12/2008
• Est. Priority Date: 11/15/2006
• 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: DenBaars, Steven P., Keller, Stacia, David, Aurelien J. F., Weisbuch, Claude C. A.
• Granted Patent: US 7,977,694 B2
• 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 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Light Emitting Diodes (LEDs) where the emission region, usually a (Al,In,Ga)N layer, is structured for efficient light extraction, are disclosed. The structuring is designed for light extraction from thin films, such as a photonic crystal acting as a diffraction grating. In addition, the structuring controls the in-plane emission and allows new modes into which light will be emitted. Various electrode designs are proposed, including ZnO structures which are known to lead to both excellent electrical properties, such as good carrier injection, and high transparency. Alternatively, the (Al,In,Ga)N layer can be replaced by structures with other materials compositions, in order to achieve efficient light extraction.

Claims

1. A light emitting diode (LED), comprising:

a structured emitting region including one or more active layers embedded in a plurality of index modulation layers, wherein the index modulation layers are structured as a photonic crystal; and

a p-type contact and an n-type contact on the LED for applying a bias across the contacts.

2. The LED of claim 1, wherein the index modulation layers include a lower index layer and a higher index layer, and the active layer is positioned inside the lower index layer.

3. The LED of claim 2, wherein the LED has an emission rate 60% to 80% of an emission rate for a non structured emitting region comprised of the higher index layer.

4. The LED of claim 1, wherein the p-type contact or the n-type contact is a transparent electrode.

5. The LED of claim 4, wherein the transparent electrode comprises zinc oxide, silicon carbide or indium tin oxide.

6. The LED of claim 1, wherein the p-type contact or the n-type contact is a reflective contact.

7. The LED of claim 1, wherein the structured emitting region comprises (Al,Ga,In)N.

8. The LED of claim 1, further comprising a backside mirror positioned on a surface of the LED.

9. The LED of claim 1, further comprising a regrown GaN layer between the structured emitting region and the p-type contact or the n-type contact for improving electrical contact, optical properties or both.

10. The LED of claim 1, further comprising a structured lateral epitaxial grown region below or on top of the structured emitting region.

11. The LED of claim 1, further comprising materials filling holes in the photonic crystal.

12. The LED of claim 11, wherein the material filling the holes is dielectric, metal, semiconductor, or optically active such as light emitting polymers or dyes.

13. The LED of claim 1, wherein the photonic crystal has a non-regular pattern.

14. The LED of claim 1, wherein the photonic crystal has a periodic pattern.

15. The LED of claim 1, wherein the photonic crystal has a pattern optimised for directional light emission.

16. A method for fabricating a light emitting diode (LED) having efficient light extraction, comprising

forming a structured emitting region including one or more active layers embedded in a plurality of index modulation layers, wherein the index modulation layers are structured as a photonic crystal;

and

forming both a p-type contact and an n-type contact on the LED for applying a bias across the contacts.

17. The method of claim 16, wherein the structured emitting region is formed by etching or direct organized growth.

18. The method of claim 16, further comprising forming a reflective contact on top of the structured emitting region.

19. The method of claim 16, further comprising forming a transparent contact by direct deposition or attachment of a thin conductive and transparent layer on top of the structured emitting region.

20. The method of claim 16, further comprising removing the LED from a substrate.

21. The method of claim 16, further comprising thinning the structured emitting region.

22. The method of claim 16, further comprising growing or regrowing GaN on top of the structured emitting region.

23. The method of claim 16, further comprising growing an additional lateral epitaxial overgrowth (LEO) grown structured layer below or on top of the structured emitting region.

24. The method of claim 16, wherein the structured emitting region provides for light extraction from thin films, such as the photonic crystal acting as a diffraction grating.

25. The method of claim 16, wherein the structured emitting region controls in-plane emissions and allows new modes into which light will be emitted.