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Growth of large aluminum nitride single crystals with thermal-gradient control

  • US 9,028,612 B2
  • Filed: 06/30/2011
  • Issued: 05/12/2015
  • Est. Priority Date: 06/30/2010
  • Status: Active Grant
First Claim
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1. A method of forming single-crystal aluminum nitride (AlN), the method comprising:

  • providing a plurality of thermal shields comprising (i) a first thermal shield defining a first opening therethrough and (ii) a second thermal shield defining a second opening therethrough larger than the first opening;

    arranging the plurality of thermal shields over the lid of a growth chamber such that the first thermal shield is disposed between the lid of the growth chamber and the second thermal shield;

    initiating the formation of an AlN single crystal substantially at a single growth center within the growth chamber proximate the lid of the growth chamber, a location of the single growth center being determined at least in part by a location of the first opening in the arranged first thermal shield;

    condensing vapor comprising aluminum and nitrogen within the growth chamber, thereby increasing a size of the AlN single crystal along a growth direction; and

    during formation of the AlN single crystal, forming and maintaining, within the growth chamber and at least in part via arrangement of the plurality of thermal shields outside of the growth chamber, (i) a first non-zero thermal gradient in a direction substantially parallel to the growth direction and (ii) a second non-zero thermal gradient in a direction substantially perpendicular to the growth direction,wherein a ratio of the first thermal gradient to the second thermal gradient is less than 10.

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