Low-resistance contacts for p-type monolayer tungsten diselenide transistors using metallic layered Nb_0.3W_0.7Se₂

Abstract

Achieving low contact resistance is a critical challenge in the development of p-type transistors that use monolayer transition metal dichalcogenides, such as tungsten diselenide (WSe2), as their channel material. Contacts made with high work function metals require deposition at high temperatures, which typically creates defects or strain at the metal–channel interface. One solution is to use metallic two-dimensional (2D) materials that have atomically flat surfaces and can be deposited at low temperatures, as have been reported for n-type semiconductors. However, the comparatively large bandgap of WSe2 has hindered experimental progress with p-type transistors. Here we show that metallic layered Nb0.3W0.7Se2 can be used to create contacts for monolayer and bilayer WSe2 field-effect transistors with channel lengths down to 100 nm. Our 2D–2D contacted field-effect transistors exhibit on-current densities of up to 358 µA µm−1 and 1.1 mA µm−1 on monolayer and bilayer WSe2 channels, respectively. In combination with scaled gate dielectrics (effective oxide thickness of 1.3 nm), the fabricated 2D–2D contacted monolayer WSe2 devices achieve a subthreshold swing of 88 mV dec−1.