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.Comment: 4 pages, 4 figures, submitted for Applied Physics Letter
