Superconductivity and Field Effect Transistors

A gate-controlled semiconductor-coupled proximity effect weak link acts as a superconducting field effect transistor (FET). In this paper we present a semi-quantitative analysis of the static electrical properties of such a device, comparing theory and available experimental measurements. We emphasize that the critical current-resistance product, an important figure of merit for potential applications, is often significantly larger than that expected from theory. We offer an explanation for this discrepancy and describe experiments in progress to test it. Our analysis can be used to discuss the feasibility, advantages, and disadvantages of these devices, both for scientific investigations and for applications, allowing comparison of the potential of superconducting FETs with more familiar normal FETs.