Low-temperature p-type ohmic contact to WSe2 using p+-MoS2/WSe2 van der Waals interface

Abstract

This study demonstrates a low-temperature Ohmic contact to WSe2 using a van der Waals (vdW) junction between highly p-doped MoS2 (p+-MoS2) and WSe2. p+-MoS2 exhibits a large work function comparable to that of a well-known metal such as Pt. Owing to its layered crystal structure, p+-MoS2 can easily be exfoliated to obtain atomically flat, freshly cleaved surfaces. Moreover, it is stable in air; therefore, this material can be used as an efficient hole-injection contact to a transition metal dichalcogenide semiconductor like WSe2. An h-BN encapsulated WSe2 field effect transistor (FET) was fabricated, having electrical contacts in the form of two flakes of exfoliated p+-MoS2. The fabricated FET demonstrated Ohmic contact behavior under hole doping between room temperature (295 K) and liquid helium temperature (4.2 K). Further, owing to the low contact resistance of the p+-MoS2/p-WSe2 junction, metal-to-insulator transition of WSe2 was observed upon hole doping, as well as quantum oscillation under the application of a magnetic field. On the basis of the Arrhenius plot, a potential barrier height of ∼41 meV at the p+-MoS2/p-WSe2 junction was determined; we infer that this value is limited by the carrier depletion region of p+-MoS2 at the junction. Overall, this appears to indicate potential high performance of the p+-MoS2/WSe2 vdW Ohmic contact.