Performance metrics of current transport in pristine graphene nanoribbon field-effect transistors using recursive non-equilibrium Green's function approach

Abstract

Graphene nanoribbons (GNRs) are an emerging material for future nanoelectronic applications. Because GNR fabrication technology is still in an early stage, modelling of GNR field-effect transistors (GNRFETs) is significant for evaluating the performance metrics of these devices. In this study, the charge transport properties of double-gate monolayer GNRFETs with various channel widths and lengths and doped contacts are investigated. The Hamiltonian matrix of the device is derived using the nearest-neighbour tight-binding method. The self-consistent solutions of the Poisson and Schrödinger equations are obtained within a recursive non-equilibrium Green's function formalism using the successive over-relaxation method to reduce the time required for the simulation. The effects of channel length and width of the device on the electronic transport properties such as the total density of states, transmission coefficient, energy-resolved current spectrum, and current–voltage characteristics are investigated. The performance metrics of the device, including the subthreshold swing, drain-induced barrier lowering (DIBL), threshold voltage, and on/off current ratio, are computed. It is found that for narrower and longer devices, the subthreshold swing and DIBL decrease, whereas the on/off current ratio increases. In addition, when the width index is in the 3p + 1 family, the device exhibits better switching performance. 7-armchair GNRFETs at 7 nm exhibits an outstanding subthreshold swing of ~67 mV/dec and a DIBL of ~54 mV/V. Thus, the narrower and longer device is less affected by short-channel effects, and the lower leakage current during the off state enables better switching performance, making it a potential candidate for future nanoelectronic applications in low-power design.