▎ 摘　　要

High-frequency performance of graphene field-effect transistors (GFETs) has been limited largely by parasitic resistances, including contact resistance (R-C) and access resistance (R-A). Measurement of short-channel (500 nm) GFETs with short (200 nm) spin-on-doped source/drain access regions reveals negligible change in transit frequency (f(T)) after doping, as compared to similar to 23% f(T) improvement for similarly sized undoped GFETs measured at low temperature, underscoring the impact of R-C on high-frequency performance. DC measurements of undoped/doped short and long-channel GFETs highlight the increasing impact of R-A for larger GFETs. Additionally, parasitic capacitances were minimized by device fabrication using graphene transferred onto low-capacitance quartz substrates. (C) 2014 AIP Publishing LLC.