  Using 2-D self-consistent ballistic quantum transport simulations, we
investigate the short-channel behavior of graphene field-effect transistors and
its impact on the device transconductance and subsequently the intrinsic
cut-off frequency (fT). Although with thin oxides, fT expectedly scales
inversely with the gate length, significant band-to-band tunneling at OFF state
leads to a departure from this trend in case of thick oxides. We also examine
the effect of achieving better electrostatics at the cost of increased gate
capacitance and illustrate that this can indeed degrade the fT. These
considerations should be implicit in the optimization of graphene transistors
for high-frequency applications.
