Narrow-band-gap base transistor structure with dual collector-base

Abstract

A semiconductor structure, in the form of a resonant-tunneling transistor employs a quantum well region which is at a lower potential than the conduction band edge in the contacts, as a result of the lower band gap of InGaAs relative to GaAs. Thus, the first energy level in the well lies below the conduction band edge in the contact, and therefore base electrons are retained in bond states. In addition, the base-collector barrier is extended by a gradient of Al.sub.x Ga.sub.1-x As. In the specific embodiment, the barrier is extended by some 300 .ANG., and the proportion of Al decreases away from the barrier until only n.sup.+ GaAs is present. In this manner, tunneling current between the base and collector is significantly reduced, without adversely affecting emitter-collector tunneling current. The structure described herein can be used in a variety of materials, and transistor structures, such as the induced base transistor, in addition to the resonant-tunneling transistor.