  Inelastic phonon scattering in graphene field-effect transistors (FETs) is
studied by numerically solving the Boltzmann transport equation in three
dimensional real and phase spaces (x, kx, ky). A kink behavior due to ambipolar
transport agreeing with experiments is observed. While low field behavior has
previously been mostly attributed to elastic impurity scattering in earlier
studies, it is found in the study that even low field mobility is affected by
inelastic phonon scattering in recent graphene FET experiments reporting high
mobilities . As the FET is biased in the saturation regime, the average carrier
injection velocity at the source end of the device is found to remain almost
constant with regard to the applied gate voltage over a wide voltage range,
which results in significantly improved transistor linearity compared to what a
simpler model would predict. Physical mechanisms for good linearity are
explained, showing the potential of graphene FETs for analogue electronics
applications.
