High-Gain Graphene Transistors with a Thin AlOx Top-Gate Oxide

The high-frequency performance of transistors is usually assessed by speed and gain figures of merit, such as the maximum oscillation frequency fmax, cutoff frequency fT, ratio fmax/fT, forward transmission coefficient S21, and open-circuit voltage gain Av. All these figures of merit must be as large as possible for transistors to be useful in practical electronics applications. Here we demonstrate high-performance graphene field-effect transistors (GFETs) with a thin AlOx gate dielectric which outperform previous state-of-the-art GFETs: we obtained fmax/fT > 3, Av > 30 dB, and S21 = 12.5 dB (at 10 MHz and depending on the transistor geometry) from S-parameter measurements. A dc characterization of GFETs in ambient conditions reveals good current saturation and relatively large transconductance ~600 S/m. The realized GFETs offer the prospect of using graphene in a much wider range of electronic applications which require substantial gain.