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Wide Bandgap Collector Heterojunction Bipolar Transistor

IP.com Disclosure Number: IPCOM000108380D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Anantha, NG: AUTHOR [+3]

Abstract

This article describes a new Heterojunction Bipolar Transistor (HBT) using a wide energy bandgap material. The transistor is designed such that we will have a larger base-collector forward voltage than the base-emitter forward voltage. This HBT can be used to reduce power dissipation in logic circuits, to simplify logic circuits and to reduce base-collector capacitance and thereby improve performance. The material system for the proposed transistor consists of a germanium emitter, a germanium base and a gallium-arsenide collector, although other material combinations, such as Ge/Ge/Si emitter/base/collector might also be feasible.

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Wide Bandgap Collector Heterojunction Bipolar Transistor

       This article describes a new Heterojunction Bipolar
Transistor (HBT) using a wide energy bandgap material.  The
transistor is designed such that we will have a larger base-collector
forward voltage than the base-emitter forward voltage.  This HBT can
be used to reduce power dissipation in logic circuits, to simplify
logic circuits and to reduce base-collector capacitance and thereby
improve performance. The material system for the proposed transistor
consists of a germanium emitter, a germanium base and a
gallium-arsenide collector, although other material combinations,
such as Ge/Ge/Si emitter/base/collector might also be feasible.  The
concomitant fabrication process is detailed using Ultra High Vacuum
Chemical Vapor Deposition (UHV/CVD) of germanium at low temperature,
although Molecular Beam Epitaxy (MBE) may be easily substituted as an
alternative.
Fabrication Process Steps

      The following process steps are one way to form the proposed
structure:
      1.   Starting with a semi-insulating gallium arsenide
substrate, the silicon-doped 500 nm IE20 N+ sub-collector and the 200
nm 1E17 N collector are epitaxially deposited by MBE and isolation
trenches, filled with a suitable dielectric, are fabricated.
      2.   The boron-doped 100 nm 1E20 P+ germanium extrinsic base is
next deposited using UHV/CVD with 10% germane in helium.  The
extrinsic base is lithographically defined and selectively etched
using CF4 reactive ion etching (RIE). The resulting mesa is
...