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Highly efficient gallium nitride based light emitting diodes via surface roughening

外国特許コード F120006655
整理番号 E06704EP1
掲載日 2012年5月21日
出願国 欧州特許庁(EPO)
出願番号 11154566
公報番号 2320482
公報番号 2320482
出願日 平成15年12月9日(2003.12.9)
公報発行日 平成23年5月11日(2011.5.11)
公報発行日 平成28年11月16日(2016.11.16)
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
  • 03EP-0819251 (2003.12.9) EP
  • 03WO-US39211 (2003.12.9) WO
発明の名称 (英語) Highly efficient gallium nitride based light emitting diodes via surface roughening
発明の概要(英語) (EP2320482)
A gallium nitride (GaN) based light emilting diode (LED), wherein light is extracted through a nitrogen face (N-face) (42) or the LED and a surface of the N-face (42) 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 (42) 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. An (Al, Ga, In)N light emitting diode comprised
of: at least an n-type layer (42), an emitting layer (44), and a p-type layer (46); wherein light from the emitting layer (44) is extracted through a nitrogen face surface, termed "N-face surface" in the following, of the light emitting diode and the N-face surface of the light emitting diode is comprised of a cone shaped surface roughness that increases extraction efficiency of the light from the emitting layer (44) out of the N-face surface of the light emitting diode; and wherein the cone shapes of the surface roughness of the N-face surface have a size close to a wavelength of the light within the light emitting diode, so that the light within the light emitting diode is scattered or diffracted, to reduce light reflections occurring repeatedly inside the light emitting diode, thereby enhancing extraction of the light from the emitting layer (44) out of the N-face surface as compared with a light emitting diode having a flat surface.
[claim2]
2. The light emitting diode of claim 1, wherein the light from the emitting layer is extracted through the N-face surface of a layer (42) other than the emitting layer (44) of the light emitting diode.
[claim3]
3. The light emitting diode of claim 2, wherein the light from the emitting layer (44) is extracted through the N-face surface of the n-type layer (42) of the light emitting diode.
[claim4]
4. The light emitting diode of claim 3, wherein the light emitting diode is further comprised of a p-type electrode (48) on the p-type layer (46), and the p-type electrode (48) has a property of high reflection to increase light reflection toward the N-face surface of the n-type layer (42).
[claim5]
5. The light emitting diode of claim 3, wherein the light emitting diode is further comprised of an n-type electrode (92) on the n-type layer (94), and a current-blocking layer (102) is aligned under the n-type electrode (92) to keep current from concentrating below the n-type electrode (92), so that absorption of the light under the n-type electrode (92) is avoided and the extraction efficiency of the light is increased.
[claim6]
6. The light emitting diode of claim 1, wherein the light does not show any longitudinal modes.
[claim7]
7. The light emitting diode of claim 1, wherein the light emitting diode includes a current-confining frame (104) made of an insulator to restrain leakage current through sidewalls of the light emitting diode without significantly decreasing an emitting area.
[claim8]
8. The light emitting diode of claim 1, wherein the light emitting diode is mounted (52) on a high thermal conductivity material made of silicon, sapphire, SiC, diamond, AlN or various metals such as CuW.
[claim9]
9. A method of creating an (Al, Ga, In)N light emitting diode, comprising: fabricating at least an n-type layer (42), an emitting layer (44), and a p-type layer (46) of the (Al, Ga, In)N light emitting diode on or above a substrate; exposing a nitrogen face surface, termed "N-face surface" in the following, of the light emitting diode by removing the substrate from at least said layers (42, 44, 46); and fabricating cone shaped surface roughness on the exposed N-face surface of the light emitting diode to increase extraction efficiency of the light from the emitting layer (44) out of the N-face surface of the light emitting diode; wherein the cone shapes of the surface roughness of the N-face surface have a size close to a wavelength of the light within the light emitting diode, so that the light within the light emitting diode is scattered or diffracted, to reduce light reflections occurring repeatedly inside the light emitting diode, thereby enhancing extraction of the light from the emitting layer (44) out of the N-face surface as compared with a light emitting diode having a flat surface.
[claim10]
10. The method of claim 9, wherein the cone shapes of the surface roughness on the N-face surface of the light emitting diode are fabricated using an anisotropic etching, the anisotropic etching may comprise a dry etching or a photo-enhanced chemical etching, "PEC" etching.
[claim11]
11. The method of claim 9 or 10, wherein the emitting diode is in accordance with any one of claims 1 to 8.
  • 出願人(英語)
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
  • UNIVERSITY OF CALIFORNIA
  • 発明者(英語)
  • FUJII TETSUO
  • GAO YAN
  • HU EVELYN
  • NAKAMURA SHUJI
国際特許分類(IPC)
指定国 (EP2320482)
Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT RO SE SI SK TR
参考情報 (研究プロジェクト等) ERATO NAKAMURA Inhomogeneous Crystal AREA
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