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Heterojunction field effect transistor having gate threshold voltage capability

  • US 4,866,491 A
  • Filed: 01/04/1989
  • Issued: 09/12/1989
  • Est. Priority Date: 02/06/1987
  • Status: Expired due to Fees
First Claim
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1. A monocrystalline semiconductor heterojunction field effect transistor having a selectively controlled gate threshold voltage comprising:

  • a substrate having doped source and drain regions with a doping level of ≧

    1018 atoms/cm3, and a semiconductor channel region located between said source and drain regions;

    a gate insulator comprising a first undoped semiconductor material region adjacent said channel region and having a wide band gap;

    a threshold voltage controlling layer comprising a second region of semiconductor material with a narrower band gap than said first undoped semiconductor region and being different from said first undoped semiconductor material region and being separated from said channel region by said gate insulator and being doped with about 1017 to about 1019 atoms/cm3 and being a gate region;

    a third region of semiconductor material being doped with at least 2×

    1018 atoms/cm3 and being adjacent said threshold voltage controlling voltage layer and having a narrower band gap than the band gap of said threshold voltage controlling layer and being a gate region; and

    ohmic contact means to said third region.

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