Transient performance analysis of graphene FET gated via ionic solid by numerical simulations based on tight-binding method and Nernst–Planck–Poisson equations

Abstract

We investigate the electrical transport characteristics of graphene channel field-effect transistors (FETs) gated via ionic solid (IS), where the conventional gate insulator, such as SiO2, has been replaced by solid electrolytes, such as LiP3O4. In this study, we focus on (i) the gate controllability of the current in comparison to conventional graphene FETs with SiO2 as an insulating material and (ii) the transient characteristics of the drain current and time required to switch on the current. We employ the tight-binding formalism and Boltzmann equation to calculate the electronic band structure and the electronic transport in graphene, while the Nernst–Planck–Poisson equations have been employed to calculate the time-dependent charge distribution in solid electrolytes and the resulting electric double layer formation at the graphene/IS and IS/gate interfaces. Our simulations have shown that graphene FET gated via IS shows superior gate controllability more than SiO2-gated graphene FET with the insulator thickness of 1 nm, and the saturated drain current is insensitive to the IS thickness. Moreover, the time required to switch on the drain current is proportional to the thickness of IS, and the limited number of Li+ ion vacancies in IS is preferable in obtaining faster switching than the case of unlimited vacancy cases while keeping the superior gate controllability.