▎ 摘　　要

The authors report on an in-depth statistical and parametrical investigation on the microwave performance of graphene FETs on sapphire substrate. The devices differ for the gate-drain/source distance and for the gate length, having kept instead the gate width constant. Microwave S-parameters have been measured for the different devices. Their results demonstrate that the cut-off frequency does not monotonically increase with the scaling of the device geometry and that it exists an optimal region in the gate-drainlsource and gate-length space which maximises the microwave performance.