Low-temperature p-type ohmic contact to WSe_2 using p~+-MoS_2/WSe_2 van der Waals interface

摘要

This study demonstrates a low-temperature Ohmic contact to WSe_2 using a van der Waals (vdW) junction between highly p-doped MoS_2 (p~+-MoS_2) and WSe_2. p~+-MoS_2 exhibits a large work function comparable to that of a well-known metal such as Pt. Owing to its layered crystal structure, p~+-MoS_2 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 WSe_2. An h-BN encapsulated WSe_2 field effect transistor (FET) was fabricated, having electrical contacts in the form of two flakes of exfoliated p~+-MoS_2. 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~+-MoS_2/p-WSe_2 junction, metal-to-insulator transition of WSe_2 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~+-MoS_2/p-WSe_2 junction was determined; we infer that this value is limited by the carrier depletion region of p~+-MoS_2 at the junction. Overall, this appears to indicate potential high performance of the p~+-MoS_2/WSe_2 vdW Ohmic contact.