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High Performance Bipolar Transistor With A Ge EPI Base

IP.com Disclosure Number: IPCOM000048481D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Baglin, JE: AUTHOR [+2]

Abstract

A thin layer (approximately 2000 Angstrom) of Ge on single crystal Si, when annealed by a pulsed ion beam, regrows as an epitaxial layer. A Si substrate is doped, n-type, and a Ge layer, prior to annealing, is provided with p-type impurities; these regions then form the collector and base regions, respectively, of an npn bipolar transistor. An n/+/ poly layer is then selectively deposited for the emitter region of the resulting device which would provide a heterojunction emitter for the efficient injection of minority carrier electrons into the Ge base. Fabrication technology for masking, isolation and contacting is compatible with the usual technology used in the fabrication of such devices.

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High Performance Bipolar Transistor With A Ge EPI Base

A thin layer (approximately 2000 Angstrom) of Ge on single crystal Si, when annealed by a pulsed ion beam, regrows as an epitaxial layer. A Si substrate is doped, n-type, and a Ge layer, prior to annealing, is provided with p-type impurities; these regions then form the collector and base regions, respectively, of an npn bipolar transistor. An n/+/ poly layer is then selectively deposited for the emitter region of the resulting device which would provide a heterojunction emitter for the efficient injection of minority carrier electrons into the Ge base. Fabrication technology for masking, isolation and contacting is compatible with the usual technology used in the fabrication of such devices.

The performance advantages of the above device over a silicon bipolar are due to the roughly 3 times greater majority carrier mobility and minority carrier diffusion constant in Ge relative to Si. In addition, because of the heterojunction emitter, the base impurity concentration could be much higher than in Si. An improvement in switching speed of a factor of 5 over what can be achieved in Si is provided. In addition, because of the lower bandgap of Ge compared to Si, this device would turn on at a lower 0.4 eV emitter forward bias.

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