Ballistic performance limits of sub-5-nm monolayer GeS₂ and SnS₂ MOSFETs from first-principles quantum transport

Two-dimensional chalcogenide semiconductors provide an attractive platform for deeply scaled transistors because their atomically thin bodies enable strong electrostatic control and effective suppression of short-channel effects. Here, we systematically investigate the ballistic transport limits of monolayer GeS₂ and SnS₂ double-gated metal-oxide-semiconductor field-effect transistors (MOSFETs) using density functional theory combined with the nonequilibrium Green-function formalism. Both n- and p-type devices are evaluated at gate lengths of 5, 3, and 1 nm under the 2028 International Technology Roadmap for Semiconductors high-performance (HP) and low-power (LP) requirements. By optimizing the source/drain doping concentration and underlap length, the n-type armchair GeS₂ and SnS₂ MOSFETs with L_g = 5 nm deliver ultrahigh on-state currents of 5064 and 4557 µA µm^-1 for HP applications, and 1072 and 2042 µA µm^-1 for LP applications, respectively. Moreover, the intrinsic delay time and power-delay product remain well below the corresponding ITRS limits. Further analysis reveals that the excellent current-driving capability originates from the favorable balance between carrier velocity and density of states associated with the transport-direction effective mass. These findings suggest the potential of monolayer GeS₂ and SnS₂ as promising channel candidates for extending two-dimensional electronics toward the deeply scaled, energy-efficient post-silicon technology node.