Electronic, transport and ballistic device properties of quasi-one-dimensional GeS

Monolayer germanium monosulfide (GeS) is among the most promising two-dimensional (2D) materials for applications in electron devices at the nanoscale. Quasi-one-dimensional GeS nanoribbons (GeSNRs) allow a high-density integration and provide an additional avenue for tuning the material and device properties. In this work we study electronic, transport and ballistic device characteristics of sub-5 nm-wide and ~ 15 nm-long armchair and zigzag GeSNRs using quantum transport simulations based on Green’s functions, and atomically and orbitally resolved Hamiltonians obtained with density functional theory that are transformed using maximally localized Wannier functions. The evolution of bandstructure, effective mass, charge density, injection velocity, and ON-state drain current (I_ON) of GeSNRs and GeSNR-based field-effect transistors (FETs) are studied with respect to GeSNR width downscaling. We show that GeSNRs and GeSNR FETs experience strikingly different consequences of scaling and confinement depending on carrier type and edge configuration, with e.g. I_ON behavior including monotonic decrease (n- and p-type FETs with armchair GeSNRs), nearly no change (nFETs with zigzag GeSNR), and appearance of local minima and maxima (pFETs with zigzag GeSNR channels). By comparing device performance to specifications set by a technology roadmap, we demonstrate that certain GeSNR FETs can fulfil the requirements and, moreover, we provide the ranges of acceptable nanoribbon widths and equivalent oxide thickness values depending on channel type and edge configuration.