Prospects for proximity effect superconducting fets

Proximity effect superconducting field effect transistors were first proposed over a decade ago, and promising initial experimental results have been obtained recently. In this paper we address the questions of how such a device works and whether or not a useful device is feasible, issues which have been virtually ignored. We discuss the circuit implications of zero on-state resistance in a device in which the input and output voltage scales are incompatible, at least with conventional superconductors. We examine the prospects for achieving voltage gain greater than unity by using high temperature superconductors as source and drain contacts. We also discuss the constraints placed on device dimensions, operating temperature, and semiconductor materials by the natural length scale for the penetration of superconductivity into normal materials.