Small-Signal Capacitance and Current Parameter Modeling in Large-Scale High-Frequency Graphene Field-Effect Transistors

An analytical model of the small-signal current and capacitance characteristics of radio frequency graphene field-effect transistors (GFETs) is presented. The model is based on explicit distributions of chemical potential in graphene channels (including ambipolar conductivity at high source-drain bias) obtained in the framework of drift-diffusion current continuity equation solution. Small-signal transconductance and output conductance characteristics are modeled by considering the two modes of drain current saturation, including drift velocity saturation or electrostatic pinchoff. Analytical closed expression for the complex current gain and the cutoff frequency of high-frequency GFETs are obtained. This model allows to describe an impact of parasitic resistances, capacitances, interface traps on extrinsic current gain, and cutoff frequency.