Thickness-Dependent Study of High- Performance WS2-FETs With Ultrascaled Channel Lengths

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