A Novel technique for designing and optimizing gaps between graphene nanoribbons in GNRFETS using Extended Huckel Theory

Abstract By transitioning from the silicon era to emerging graphene devices, it is evident that digital electronics will need Graphene Nanoribbon Field Effect Transistors (GNRFETs) with more than one ribbon. Tuning the gap between the graphene nanoribbons in these transistors is crucial for achieving optimum and accurate structural features. This paper investigates the effect of optimizing the gap between the graphene ribbons (𝑊𝑠𝑝) of a GNRFET on the device's performance. The non-equilibrium Green's function (NEGF) technique is employed to simulate quantum transport, whereas the Extended Huckel Theory (EHT) is used for computing. Two transistors are analyzed, each comprising two identical graphene ribbons with chirality (6,0) and (7,0). Additionally investigated is the impact of varying the 𝑊𝑠𝑝 parameter on the characteristic curve, Ion/Ioff ratio and subthreshold slope, density of states, transmission spectrum, Fermi levels, and Hartree potential. Using two graphene ribbons doubles the probability of electron transition compared to a single ribbon device, according to the results. Increasing 𝑊𝑠𝑝 increases the device's on-current while decreasing its off-current. Increasing the value of 𝑊𝑠𝑝 by 1nm results in a 300% improvement in the Ion/Ioff ratio; hence, choosing values larger than 1.5 nm for 𝑊𝑠𝑝 will significantly improve the Ion/Ioff ratio. In addition, the subthreshold slope for 𝑊𝑠𝑝 values higher than 1.5 nm are quite close to the fundamental limit of 60𝑚𝑣/𝑑𝑒𝑐.