Explicit Model of Channel Charge, Backscattering, and Mobility for Graphene FET in Quasi-Ballistic Regime

Abstract

Ballistic (collision free) and drift-diffusive (collision dominated) transport mechanisms are both present in graphene, and they together contribute in the current conduction in a graphene FET (GFET). In this paper, we propose an analytical drain current model based on ballistic ( ${n}_{B}$ ) and drift-diffusive ( ${n}_{D}$ ) charge densities, backscattering coefficient ( ${R}$ ), and quasi-ballistic mobility ( $\mu _{\text {eff}}$ ). ${n}_{B}$ is calculated using the McKelvey flux theory and ${n}_{D}$ using the surface potential approach. A closed-form analytical expression is derived for the backscattering coefficient, which is valid under both low and high electric field conditions. The effective quasi-ballistic mobility is obtained by considering both scattering-dominated and scattering free mobilities. The proposed model is well aligned with experimental data, in all regions of operation, for single- and double-gate GFETs.