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 ION/IOFF 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.
@article{arxiv.1509.03896,
title = {High-Mobility Holes in Dual-Gated WSe$_2$ Field-Effect Transistors},
author = {Hema C. P. Movva and Amritesh Rai and Sangwoo Kang and Kyounghwan Kim and Babak Fallahazad and Takashi Taniguchi and Kenji Watanabe and Emanuel Tutuc and Sanjay K. Banerjee},
journal= {arXiv preprint arXiv:1509.03896},
year = {2017}
}