Browse Prior Art Database

Heterojunction Transistor

IP.com Disclosure Number: IPCOM000094540D
Original Publication Date: 1965-Feb-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Agusta, BA: AUTHOR

Abstract

This semi-conductor device uses a forward biased, radiating PN heterojunction as an emitter.

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Heterojunction Transistor

This semi-conductor device uses a forward biased, radiating PN heterojunction as an emitter.

Certain semiconductor materials, known as direct band-gap materials, can be embodied in junction devices and, when biased in a forward direction, radiate photons. Such emitted photons are transmitted through the base and generate electron-hole pairs when captured by a suitable collector.

The device shown above uses an emitter-base heterojunction, that is, a junction of different semiconductors as well as different conductivity type materials. Emitter layer 10 is a semiconductor material, e. g., Gallium Arsenide, with a P-type impurity. Base layer 12 is composed of a different semiconductor material, such as Cadmium Sulfide, with an N-type impurity. Collector 14 can be any type semiconductor material opposite in impurity type to base 12.

It is important that the emitter material be selected from a class that emits photons when biased in the forward direction, that is, direct band-gap materials. Further, it is important that the base material have a band gap substantially higher than the energy of the emitted photons, thus enabling the emitted photons to pass through the base to the collector without absorption. Moreover, the lattice constant of the base and emitter materials should be approximately equal to eliminate interface energy states.

When emitter 10 is forward biased with respect to base 12, electrons are attracted to it and radiatively co...