Spin FET Based on Graphene Nanoribbon in the Presence of Surface Roughness

In this paper, the characteristics of an armchair graphene nanoribbon spin FET (SFET) are investigated in the presence and absence of surface roughness, by employing a multiorbital tight-binding method along with the nonequilibrium Green's function approach. It is found that the bandgap monotonically decreases with increasing the vertical electric field, since Stark effect enhances spin-flip rate under a high vertical electric field. Furthermore, spin transport in the presence of a random potential, which is induced by the concurrent effect of the applied vertical electric field and surface roughness, is carefully analyzed. This random potential strongly scatters carriers and reduces spin conductance. Current-voltage characteristics of the device is studied with parallel and antiparallel contact magnetization. The results show a high dependence of spin controllability and spin flip relative current (SFRC) of the SFET on both vertical electric field and surface roughness. However, for high values of vertical electric field, SFRC is almost determined by the vertical electric field rather than surface roughness. Therefore, the proposed SFET can be widely modulated by the back-gate voltage. Results also indicate that scaling limits both SFRC and spin controllability.