Overlapping-gate architecture for silicon Hall bar field-effect transistors in the low electron density regime

Abstract

We report the fabrication and study of Hall bar field-effect transistors in which an overlapping-gate architecture allows four-terminal measurements of low-density two-dimensional 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.