Inelastic Phonon Scattering in Graphene FETs

Inelastic phonon scattering in graphene field-effect transistors (FETs) is studied by numerically solving the Boltzmann transport equation in 3-D real and phase spaces (x, k_x, k_y). 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 analog electronics applications.