Barrier-Free Carrier Injection in 2D WSe-MoSe Heterostructures via Fermi-Level Depinning.

Fermi-level pinning (FLP) at metal-semiconductor interfaces remains a key obstacle to achieving low-resistance contacts in two-dimensional (2D) transition metal dichalcogenide (TMDC)-based heterostructures. Here, we present a first-principles study of Schottky barrier formation in WSe-MoSe van der Waals heterostructures interfaced with four representative metals (Ag, Al, Au, and Pt). It was found that all metal-WSe/MoSe direct contacts induce pronounced metal-induced gap states (MIGSs), leading to significant FLP inside the WSe/MoSe band gaps and elevated Schottky barrier heights (SBHs) greater than 0.31 eV. By introducing a 2D metal-doped metallic (mWSe/mMoSe) layer between WSe/MoSe and the metal electrodes, the MIGSs can be effectively suppressed, resulting in nearly negligible SBHs for both electrons and holes, with even an SBH of 0 eV observed in the Ag-AgMoSe-MoSe contact, thereby enabling quasi-Ohmic contact behavior. Our results offer a universal and practical strategy to mitigate FLP and achieve high-performance TMDC-based electronic devices with ultralow contact resistance.