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

Abstract

Ultrascaled WS2 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}-{ mathrm{scriptscriptstyle ON}} ) and ultralow contact resistance ( {R}-{C} ) were achieved in a double-gated FET at a scaled overdrive voltage ( {V}-{OV}boldsymbol = {V}-{GS}boldsymbol-{V}-{TH} ), reaching >600 ( boldsymbol mu text{A}/boldsymbol mu text{m} ) normalized to footprint at {V}-{DS}boldsymbol =1 V and {V}-{OV}boldsymbol =2 V with a {R}-{C}∼sim ∼500 ( Omega times mu text{m} ). 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 WS2 body thickness of 2.1 nm (three layers, the thinnest in our statistics) shows the best performance in both ON-state and OFF-state.