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Highly efficient gallium nitride based light emitting diodes via surface roughening 実績あり

外国特許コード F110003757
整理番号 E06704US1
掲載日 2011年7月4日
出願国 アメリカ合衆国
出願番号 57612209
公報番号 20100025717
公報番号 8766296
出願日 平成21年10月8日(2009.10.8)
公報発行日 平成22年2月4日(2010.2.4)
公報発行日 平成26年7月1日(2014.7.1)
国際出願番号 US2003039211
国際公開番号 WO2005064666
国際出願日 平成15年12月9日(2003.12.9)
国際公開日 平成17年7月14日(2005.7.14)
優先権データ
  • 10/581,940 (2003.12.9) US
  • 2003US039211 (2003.12.9) WO
発明の名称 (英語) Highly efficient gallium nitride based light emitting diodes via surface roughening 実績あり
発明の概要(英語) A gallium nitride (GaN) based light emitting diode (LED), wherein light is extracted through a nitrogen face (N-face) of the LED and a surface of the N-face is roughened into one or more hexagonal shaped cones.
The roughened surface reduces light reflections occurring repeatedly inside the LED, and thus extracts more light out of the LED.
The surface of the N-face is roughened by an anisotropic etching, which may comprise a dry etching or a photo-enhanced chemical (PEC) etching.
特許請求の範囲(英語) [claim1]
1. A (B, Al, Ga, In)N light emitting diode (LED), comprised of: at least an n-type layer, an emitting layer, and a p-type layer;
wherein light from the emitting layer is extracted through a nitrogen face (N-face) surface of the LED and the N-face surface of the LED is comprised of structures that increase extraction efficiency of the light out of the N-face surface of the LED;
wherein the structures comprise a plurality of etched cones; and
wherein the etched cones have a size not smaller than a wavelength of the light extracted from the N-face surface.
[claim2]
2. The LED of claim 1, wherein the light from the emitting layer is extracted through the N-face surface of a layer other than the emitting layer of the LED.
[claim3]
3. The LED of claim 2, wherein the light from the emitting layer is extracted through the N-face surface of the n-type layer of the LED.
[claim4]
4. The LED of claim 3, wherein the LED is further comprised of a p-type electrode on the p-type layer, and the p-type electrode has a property of high reflection to increase light reflection toward the N-face surface of the n-type layer.
[claim5]
5. The LED of claim 3, wherein the LED is further comprised of an n-type electrode on the n-type layer, and a current-blocking layer is aligned under the n-type electrode to keep current from concentrating below the n-type electrode, so that absorption of the light under the n-type electrode is avoided and the extraction efficiency of the light is increased.
[claim6]
6. The LED of claim 1, wherein the etched cones are hexagonal shaped cones that have an angle equal to or smaller than:
2 sin-1(nair/ns)
where nair is a refractive index of air and ns is a refractive index of the N-face surface.
[claim7]
7. The LED of claim 1, wherein the etched cones are hexagonal shaped cones that have an angle equal to or smaller than:
2 sin -1(nenc/ns) ,
where nenc is a refractive index of an epoxy deposited on the N-face surface and ns is a refractive index of the N-face surface.
[claim8]
8. The LED of claim 1, wherein the n-type layer, the emitting layer and the p-type layer are each comprised of a (B, Al, Ga, In)N alloy.
[claim9]
9. The LED of claim 1, wherein the extraction efficiency of the light out of the N-face surface of the LED is increased by more than 100% as compared to the N-face surface without the structures.
[claim10]
10. The LED of claim 1, wherein the light does not show any cavity mode, interference effects, or longitudinal modes caused by a cavity formed along a growth direction of the LED.
[claim11]
11. The LED of claim 1, wherein the LED includes a current-confining frame made of an insulator to restrain leakage current through sidewalls of the LED without significantly decreasing an emitting area.
[claim12]
12. The LED of claim 1, wherein the LED is mounted on a high thermal conductivity material.
[claim13]
13. A method of creating a (B, Al, Ga, In)N light emitting diode (LED), comprising: fabricating at least an n-type layer, an emitting layer, and a p-type layer of the (B, Al, Ga, In)N LED; and
structuring a nitrogen face (N-face) surface of the LED, in order to increase extraction efficiency of the light out of the N-face surface of the LED;
wherein the structures comprised a plurality of etched cones; and
wherein the etched cones have a size not smaller than a wavelength of the light extracted from the N-face surface.
[claim14]
14. The method of claim 13, wherein the N-face surface of the LED is structured using an anisotropic etching.
[claim15]
15. The method of claim 14, wherein the anisotropic etching is a dry etching.
[claim16]
16. The method of claim 14, wherein the anisotropic etching is a wet etching.
[claim17]
17. The method of claim 16, wherein the wet etching is a photo-enhanced chemical (PEC) etching.
[claim18]
18. The method of claim 13, wherein the structuring of the N-face surface of the LED comprises roughening or patterning the N-face surface of the LED.
[claim19]
19. The method of claim 13, wherein the light from the emitting layer is extracted through the N-face surface of a layer other than the emitting layer of the LED.
[claim20]
20. The method of claim 19, wherein the light from the emitting layer is extracted through the N-face surface of the n-type layer of the LED.
[claim21]
21. The method of claim 20, wherein the LED is further comprised of a p-type electrode on the p-type layer, and the p-type electrode has a property of high reflection to increase light reflection toward the N-face surface of the n-type layer.
[claim22]
22. The method of claim 20, wherein the LED is further comprised of an n-type electrode on the n-type layer, and a current-blocking layer is aligned under the n-type electrode to keep current from concentrating below the n-type electrode, so that absorption of the light under the n-type electrode is avoided and the extraction efficiency of the light is increased.
[claim23]
23. The method of claim 13, wherein the etched cones are hexagonal shaped cones that have an angle equal to or smaller than:
2 sin-1(nair/ns )
where nair is a refractive index of air and ns is a refractive index of the N-face surface.
[claim24]
24. The method of claim 13, wherein the etched cones are hexagonal shaped cones that have an angle equal to or smaller than:
2 sin-1(nenc/ns)
where nenc is a refractive index of an epoxy deposited on the N-face surface and ns is a refractive index of the N-face surface.
[claim25]
25. The method of claim 13, wherein the n-type layer, the emitting layer and the p-type layer are each comprised of a (B, Al, Ga, In)N alloy.
[claim26]
26. The method of claim 13, wherein the extraction efficiency of the light out of the N-face surface of the LED is increased by more than 100% as compared to the N-face surface without the structures.
[claim27]
27. The method of claim 13, wherein the light does not show any cavity mode, interference effects, or longitudinal modes caused by a cavity formed along a growth direction of the LED.
[claim28]
28. The method of claim 13, wherein the LED includes a current-confining frame made of an insulator to restrain leakage current through sidewalls of the LED without significantly decreasing an emitting area.
[claim29]
29. The method of claim 13, wherein the LED is mounted on a high thermal conductivity material.
[claim30]
30. The LED of claim 1, wherein the LED includes a substrate, and the N-face surface is structured after being exposed by removing the substrate from the LED.
[claim31]
31. The method of claim 13, wherein the LED includes a substrate, and the N-face surface is exposed before structuring by removing the substrate from the LED.
[claim32]
32. The LED of claim 1, wherein the LED includes a GaN substrate, and the N-face surface is the N-face surface of the GaN substrate.
[claim33]
33. The method of claim 13, wherein the LED includes a GaN substrate, and the N-face surface is the N-face surface of the GaN substrate.
  • 発明者/出願人(英語)
  • FUJII TETSUO
  • GAO YAN
  • HU EVELYN L
  • NAKAMURA SHUJI
  • UNIVERSITY OF CALIFORNIA
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 257/95
  • 257/98
  • 257/E33.074
参考情報 (研究プロジェクト等) ERATO NAKAMURA Inhomogeneous Crystal AREA
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