Limiting factors for optical switching using nano-structured graphene-based field effect transistors

Thanks to the particular band diagram of graphene, it is recognized as a promising material for developing optoelectronic devices at the nano-scale. In this paper, a functional stack comprised of graphene and other materials is numerically investigated to extract the related capacitance-voltage curve by taking into account practical considerations regarding the nano-structured electronic devices. Polycrystalline silicon gates are used as electrical contacts in this stack, which are considered as semiconductor materials rather than metal contacts owing to the nano-scale dimensions of the constitutive materials. Moreover, graphene is effectively modeled to highlight its presence in the stack. Then, the stack is developed for the construction of a graphene field effect transistor (GFET) in order to examine the speed response of the stack. In this regard, by selecting the carrier mobility of 1500  cm²/(V·s) for graphene and a particular bias condition, the small-signal current gain of the GFET is computed so that according to the simulation results, the intrinsic cutoff frequency of 13.89 GHz is achieved.