Causes of asymmetry in graphene transfer characteristics

Back-gated graphene field-effect transistor (FET) with Carrier mobility values over 8000 cm²/Vs is fabricated. Contact resistances and carrier motilities are extracted from an established model. We investigate the asymmetry in its transfer characteristics and attribute it to the differences in contact resistances modulated by the back gate voltages and distinct mobility of electrons and holes. The experimental results are analyzed quantitatively and the mechanisms are discussed.