Thickness-Dependent Study of High- Performance WS 2 -FETs With Ultrascaled Channel Lengths

Ultrascaled WS2field-effect transistors (FETs) fabricated on exfoliated multilayer channels with excellent ON-state and OFF-state performance are reported. Recorded high ON-state current ( I ON) and ultralow contact resistance ( RC) were achieved in a double-gated FET at a scaled overdrive voltage ( VOV=VGS-VTH), reaching >600 ( μ /μ ) normalized to footprint at VDS=1 V and VOV=2 V with a RC~ 500 ( Ω×μ). We report statistics of more than 50 FETs with varying channel lengths, showing excellent OFF-state behavior with small threshold voltage ( VTH) variations, near-ideal subthreshold slope (SS), and small drain-induced barrier lowering (DIBL). Various channel thicknesses ( TCH) ranging from 2.1 to 7 nm were carefully evaluated in terms of short channel effects (SCEs) and ON-state current, and a WS2body thickness of 2.1 nm (three layers, the thinnest in our statistics) shows the best performance in both ON-state and OFF-state.