▎ 摘　　要

A study is performed on the contact length scaling in graphene field effect transistors. When the contact length (L-C) is below the transfer length (L-T), both transconductance and on-current increase rapidly with L-C due to the strengthened carrier injection. Over the transfer length, the transconductance keeps increasing prominently before coming to a saturation. A possible explanation is that larger contact length would induce deeper doping in graphene, and the nonlinear screening of metal-induced charge could modify the potential barrier, which subsequently adjusts the contact resistance and transconductance. In principle, the electron-hole asymmetry can be tuned via altering the contact lengths. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3691629]