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Low sheet resistance GaN channel on Si substrates using InAlN and AlGaN bi-layer capping stack

  • US 9,660,064 B2
  • Filed: 12/26/2013
  • Issued: 05/23/2017
  • Est. Priority Date: 12/26/2013
  • Status: Active Grant
First Claim
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1. A method to form transistor layers comprising:

  • forming a GaN channel layer comprising (1) GaN material on a top surface of a substrate (2) a capping AlN layer that has a thickness of between 0.6 and 1.5 nanometers on the GaN material, wherein the GaN channel layer includes islands of GaN material formed between islands that consist of oxide material only that are completely buried under a thickness of the GaN material;

    forming a bi-layer capping stack on a top surface of the GaN channel layer, wherein forming the bi-layer capping stack includes;

    forming a lower capping AlGaN layer of AlGaN material on a top surface of a capping AlN layer comprising AlN material and excluding Indium formed on the top surface of the GaN channel layer; and

    forming an upper capping AlInN layer of AlInN material on a top surface of the AlGaN material, wherein the AlGaN layer comprises AlXGa(1-X)N, where X is less than 0.4; and

    wherein the AlInN layer is AlYIn(1-Y)N, where Y is greater than 0.8, wherein a top surface of the AlGaN material forms a setback material surface upon which the AlInN material may be selectively etched, wherein the AlGaN layer has a thickness of between 2 and 10 nm, and causes an electron density of greater than 2.5 E13 cm/2; and

    wherein the AlInN layer has a thickness of between 5 and 15 nm, and causes a channel mobility of between 900 and 1000 CM2/V-s, wherein the bi-layer capping stack causes a sheet resistance of between 200 and 300 ohms per SQR in a 2DEG channel formed in a upper thickness of the GaN layer.

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