▎ 摘　　要

Theoretical investigation demonstrates that the current-voltage characteristics of a metal/graphene nanoribbon with donor impurities contact under forward bias condition has typical properties of a metal/silicon contact. Assuming that the work function of graphene nanoribbon will not change with its width, the results demonstrate that under a given biasing voltage, the current density of the contact decreases with the decrement of the nanoribbon width. Such a current-density decrement is especially large when the graphene-nanoribbon width drops to the few nanometers range. Furthermore, the high-energy electron density increases with the decrement of the nanoribbon width, which also impacts the current density significantly. Therefore, the relationship between the decrement of the current density and the nanoribbon width is non-exponential. The results in this paper also illustrate that the current density of metal/graphene nanoribbon contact at a given biasing voltage increases slowly with the increment of the donor density.