▎ 摘　　要

We present a numerical study of the current-voltage characteristics in zigzag-edged graphene nano-ribbon (Z-GNR) devices. Our calculations employing the non-equilibrium Green's function method and the density-functional tight-binding method show that the Z-GNR with transverse symmetry can exhibit remarkable current saturation behavior in spite of the absence of the bandgap. We further demonstrate that the saturation current can be controlled by the additional doping in the channel region. The mechanism of such current saturation can be explained in terms of the symmetry of the wavefunctions corresponding to the conduction and the valence bands in Z-GNR.