▎ 摘　　要

The ultrahigh-frequency (from several GHz to THz) performance of a graphene nanoribbon field-effect transistor (GNRFET) is analyzed using a semiquantum analytical model. The results indicate that the use of a high-k gate dielectric layer to improve the performance also increases the parasitic internal fringe capacitance. This limits the operation of the GNRFET in the higher frequency range. Hence, a design for a GNRFET structure with a combination of different gate dielectric layers is proposed to minimize the effect of the parasitic capacitance. The calculations based on the model illustrate that the proposed device could be used for high-frequency applications even in the THz range without compromising the figures of merit.