Radio-Frequency Transistors Using Chemical-Vapor-Deposited Monolayer Graphene: Performance, Doping, and Transport Effects

Large-area graphene is synthesized by Cu-catalyzed chemical vapor deposition (CVD), transistors are constructed, and the dc/RF performance is examined. Top-gate transistors, i.e., with a gate length of 3 μm and V
_ds
= 5 V, have a peak dc transconductance in excess of 20 mS/mm and a drive current of 0.5 A/mm. RF measurements achieve gigahertz extrinsic current-gain cutoff frequency with low back biasing. Back-gated devices are used to examine doping and transport effects that impact the performance. Good agreement between measurements and a drift-diffusion model is obtained for gapless graphene with a net p-type doping and asymmetric electron/hole mobility. The mean free path for scattering is extracted and reveals that the transport suffers from large levels of Coulomb scattering and short-range scattering. The results are of importance for understanding the performance potential of large-area CVD graphene in future RF devices.