High performance ultrascaled monolayer/bilayer WSe2 FETs achieved by immaculate 2D/2D contacts

Abstract Achieving low contact resistance in p-type transistors remains a critical challenge when using transition-metal dichalcogenides (TMDs) as channel materials. Deposition of high work function contact metals at elevated temperatures often causes defects or strain at the metal/channel interface, which in turn can result in an increased contact resistance. Metallic two-dimensional (2D) materials offer a promising solution in this context due to their low-temperature contact formation and atomically flat surfaces. However, experimental progress has been slow in part due to the rather large bandgap of monolayer WSe 2 . Here, we report a novel approach, using metallic layered Nb 0.3 W 0.7 Se 2 as a contact for monolayer and bilayer WSe 2 transistors with channel lengths down to 100 nm. Combined with ultra-scaled gate dielectrics with an effective oxide thickness (EOT) of 1.3nm, the resulting 2D/2D contacted FETs exhibit high on-current densities of up to 375 µA/µm and 1.1 mA/µm on monolayer and bilayer WSe 2 channel, respectively. This method also enables the fabrication of 2D/2D contacted monolayer WSe 2 devices achieving subthreshold swings as small as 88 mV/dec.