▎ 摘　　要

An empirical model is developed to characterize metal-contact effects on the transfer characteristics of graphene field-effect transistors. The present model is based on a diffusive transport, and considers charge carrier doping from metallic electrodes to the adjacent graphene channel. An electron-hole conductivity asymmetry, one of the main features in the transfer characteristics, is well reproduced by the model. Model calculations with varied parameters show that the conductivity asymmetry becomes more distinct with higher charge-carrier mobility, higher doping level at the metal contacts, larger extent of the doped region near the contacts, or shorter channel lengths. (C) 2011 The Japan Society of Applied Physics