High-Mobility Holes in Dual-Gated WSe₂ Field-Effect Transistors

2015/09/13 by Hema C. P. Movva, Amritesh Rai, Sangwoo Kang +6 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.mtrl-sci

paper · pdf · doi:10.1021/acsnano.5b04611

published as ACS Nano, 9 (10), pp 10402-10410 (2015) · 18 pages, 5 figures, 7 supporting figures, ACS Nano 2015

arxiv created 2015/09/13 · arxiv updated 2017/02/21

Abstract

We demonstrate dual-gated p-type field-effect transistors (FETs) based on few-layer tungsten diselenide (WSe₂) using high work-function platinum source/drain contacts, and a hexagonal boron nitride top-gate dielectric. A device topology with contacts underneath the WSe₂ results in p-FETs with I_ON/I_OFF ratios exceeding 10⁷, and contacts that remain Ohmic down to cryogenic temperatures. The output characteristics show current saturation and gate tunable negative differential resistance. The devices show intrinsic hole mobilities around 140 cm²/Vs at room temperature, and approaching 4,000 cm²/Vs at 2 K. Temperature-dependent transport measurements show a metal-insulator transition, with an insulating phase at low densities, and a metallic phase at high densities. The mobility shows a strong temperature dependence consistent with phonon scattering, and saturates at low temperatures, possibly limited by Coulomb scattering, or defects.

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