Validity of the Ballistic Top-of-the-Barrier Model for FETs Based on 2D Material Nanoribbons

We investigate our in-house implementation of the non-equilibrium Green’s function (NEGF) formalism in combination with the top-of-the-barrier (ToB) ballistic model, as implemented in our QUDEN (from Quantumtransport Device Engineering in Nanoelectronics) simulator. We calibrate QUDEN on self-consistent NEGF-Poisson simulations of graphene nanoribbon (GNR) field-effect transistor (FET) with $\sim 15 \mathrm{~nm}$ channel in the commercial software QuantumATK. It is demonstrated that QUDEN device predicting ability is adequate for nanoribbon-based FETs, except in materials with ultra-low effective mass. QUDEN is then employed to explore monolayer zirconium-disulfide $\left(\mathrm{ZrS}_{2}\right)$ nanoribbon $\left(\mathrm{ZrS}_{2} \mathrm{NR}\right)$ nFETs, using Hamiltonians from density functional theory (DFT) calculations. We show that $\mathrm{ZrS}_{2} \mathrm{NR} \mathrm{nFET}$ exhibits $32 \%$ lower ON-state current compared to GNR nFET, which is attributed to $36 \%$ higher electron effective mass in ZrS
2
NRs than in GNRs. Our results show that DFT-based Hamiltonians and NEGF-ToB model can be efficiently used for accurate investigation of nanoribbon-based devices.