▎ 摘　　要

This paper demonstrates high frequency performance of graphene transistors grown by chemical vapor deposition on copper foils. Using Ti/Pd/Au-based ohmic contacts and a hybrid gate dielectric stack of 5 nm SiO(2) and 15nm Al(2)O(3) grown by atomic layer deposition, graphene transistors with an extrinsic current-gain cut-off frequency (f(T)) of 2 GHz and power-gain cut-off frequency, f(max), of 5.6GHz were obtained for a gate length of L(g) = 1.6 mu m. By applying a bias to the Si substrate the access resistances are reduced, which improved the fT and fmax in the devices to 3.5 and 6.5 GHz, respectively. Finally we demonstrate these devices in a real-application circuit for binary-phase shift keying. (C) 2011 The Japan Society of Applied Physics