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Device including transparent layer with profiled surface for improved extraction

  • US 10,319,881 B2
  • Filed: 12/26/2016
  • Issued: 06/11/2019
  • Est. Priority Date: 06/15/2011
  • Status: Active Grant
First Claim
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1. A device comprising:

  • a group III nitride heterostructure; and

    an at least partially transparent substrate having a first side and a second side, wherein the group III nitride heterostructure is located on the second side, and wherein radiation passes through the second side, and wherein the second side comprises a profiled surface, the profiled surface including;

    a plurality of large roughness components providing a first variation of the profiled surface having a characteristic scale approximately an order of magnitude larger than a target wavelength of the radiation, wherein the plurality of large roughness components comprise a series of truncated shapes formed of a material of the at least partially transparent substrate, wherein at least one of the series of truncated shapes is inversely truncated with respect to a direction the radiation travels through the at least partially transparent substrate; and

    a plurality of small roughness components providing a second variation of the profiled surface having a characteristic scale on the order of the target wavelength of the radiation, wherein the plurality of small roughness components are superimposed on the plurality of large roughness components, wherein a graded refractive index along a height of each small roughness component in the plurality of small roughness components decreases substantially linearly along the height.

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