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

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.