Transport behaviors in graphene field effect transistors on boron nitride substrate

We model the transport behavior of a top-gated graphene field-effect transistor where boron nitride is used as substrate and gate insulator material. Our simulation model is based on the non-equilibrium Green´s function approach to solving a tight-binding Hamiltonian for graphene, self-consistently coupled with Poisson´s equation. The analysis emphasizes the effects of the chiral character of carriers in graphene in the different transport regimes including Klein and band-to-band tunneling processes. We predict the possible emergence of negative differential conductance and investigate its dependence on the temperature and the BN-induced bandgap. Short-channel effects are evaluated from the analysis of transfer characteristics as a function of gate length and gate insulator thickness. They manifest through the shift of the Dirac point and the appearance of current oscillations at short gate length.