Tuning contact properties in MoSi₂N₄ van der Waals heterostructures with Janus metals: realizing Ohmic contacts

A low Schottky barrier height and high carrier tunneling probability are key figures of merit for charge transport at two-dimensional (2D) semiconductor heterojunctions. 2D MoSi₂N₄, with high carrier mobility and excellent stability, has emerged as a promising channel material for high-performance field-effect transistors (FETs). In this work, we investigate the contact mechanisms between 2D MoSi₂N₄ and MoSi₂N₄-derived Janus metals (MoSi₂N₃P₁, denoted as M1; MoSi₂N₂P₂, M2; MoSi₂N₂As₂, M3; and MoSi₂NAs₃, M4) through first-principles calculations. Electronic structure analysis reveals that the M2B-MSN heterostructure (meaning that the bottom side of M2 contacts with MoSi₂N₄) forms a quasi-p-type Ohmic contact, while the M1B-MSN heterostructure exhibits an n-type Ohmic contact at the vertical interface with a tunneling probability, as further supported by calculations of interfacial charge transfer and redistribution. Quantum transport simulations further confirm Ohmic behavior at the M1B-MSN interface. These findings provide a theoretical basis for designing MoSi₂N₄-based FETs with optimized contacts.