Interface steps in field effect devices

TL;DR

This paper investigates how interface steps in field effect transistors affect electronic properties, revealing exponential suppression of transmission and potential for weak links in superconducting devices, with implications for high-doping FET engineering.

Contribution

It provides a theoretical analysis of the electronic effects of interface steps in FETs using the Thomas-Fermi approximation, highlighting potential device challenges and opportunities.

Findings

Transmission through steps is exponentially suppressed by electric field and step height.

Field enhancement at step edges can cause electric breakthrough of insulating layers.

Steps can form weak links and atomic size Josephson junctions in superconducting FETs.

Abstract

The charge doped into a semiconductor in a field effect transistor (FET) is generally confined to the interface of the semiconductor. A planar step at the interface causes a potential drop due to the strong electric field of the FET, which in turn is screened by the doped carriers. We analyze the dipolar electronic structure of a single step in the Thomas-Fermi approximation and find that the transmission coefficient through the step is exponentially suppressed by the electric field and the induced carrier density as well as by the step height. In addition, the field enhancement at the step edge can facilitate the electric breakthrough of the insulating layer. We suggest that these two effects may lead to severe problems when engineering FET devices with very high doping. On the other hand steps can give rise to interesting physics in superconducting FETs by forming weak links and potentially creating atomic size Josephson junctions.