Overlapping-gate architecture for silicon Hall bar MOSFET devices in the low electron density regime

TL;DR

This paper introduces an overlapping-gate architecture for silicon Hall bar MOSFET devices, enabling low-density 2D electron system measurements with improved contact density and resistance, despite some mobility reduction.

Contribution

The study presents a novel overlapping-gate design that allows low-density measurements in MOSFETs while maintaining high contact density, advancing low-electron-density device characterization.

Findings

Enables measurements at lower electron densities

Allows high channel resistances in experiments

Identifies voltage threshold shift due to oxide charge

Abstract

We report the fabrication and study of Hall bar MOSFET devices in which an overlapping-gate architecture allows four-terminal measurements of low-density 2D electron systems, while maintaining a high density at the ohmic contacts. Comparison with devices made using a standard single gate show that measurements can be performed at much lower densities and higher channel resistances, despite a reduced peak mobility. We also observe a voltage threshold shift which we attribute to negative oxide charge, injected during electron-beam lithography processing.