Browse Prior Art Database

SISFET with Reduced Gate to Drain Leakage

IP.com Disclosure Number: IPCOM000109540D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 173K

Publishing Venue

IBM

Related People

Frank, DJ: AUTHOR

Abstract

Described is a way to reduce the gate to drain reverse leakage current of GaAs/AlGaAs SISFETs. The reduction is achieved by etching away the AlGaAs on the drain side of the gate before implanting the drain region with dopants.

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This is the abbreviated version, containing approximately 52% of the total text.

SISFET with Reduced Gate to Drain Leakage

       Described is a way to reduce the gate to drain reverse
leakage current of GaAs/AlGaAs SISFETs.  The reduction is achieved by
etching away the AlGaAs on the drain side of the gate before
implanting the drain region with dopants.

      In conventional SISFET design, the AlGaAs insulating layer
remains over the source and drain regions after the gate has been
defined by etching, as shown on the source side of the figure.  The
AlGaAs is implanted into and annealed, and becomes part of the source
and drain in those regions.  This is advantageous on the source side,
since it keeps the surface states on the exposed AlGaAs surface far
away from the active channel region, and thus provides low source
resistance.

      On the drain side, however, the conventional design results in
a relatively large gate to drain leakage current when the drain is
biased high and the gate is biased below threshold.  This is because
the field extracting carriers from the gate is quite high under these
circumstances.  The high field causes leakage in two ways: it causes
an accumulation layer in the gate which lowers the barrier for
thermionic emission of carriers toward the drain, and it enhances the
tunnelling probability for carriers tunnelling out of the gate toward
the drain.

      The high gate to drain leakage current can be considerably
decreased by removing the AlGaAs on the drain side of the gate before
implantation, as shown in the figure.  This causes the doping to be
moved further from the gate edge, and thus reduces the electric...