2D Electron Gas‐Induced the Lowered Tunneling Barrier and Ohmic Behavior Simultaneously in 2D Metal‐Semiconductor Contacts

Abstract 2D materials have the advantages of dangling‐bond‐free interfaces, facilitating Fermi‐level depinning, and could be utilized for achieving ohmic contacts in metal‐semiconductor contacts. However, the additional tunneling barrier, resulting from the large van der Waals (vdW) gap, limits the injection of electrons at the interfacial region. Herein, benefitting from the ultralow work functions and the electron‐rich characteristic of 2D electrides, the formation of quasi‐bonds at the heterogeneous interface can significantly suppress the tunneling barriers and realize Ohmic contacts simultaneously based on 2D electrides and 2D semiconductors, such as MSi 2 N 4 (M = Cr, Hf, Mo, Ti, V, and Zr) and common transition‐metal dichalcogenides (MoS 2 , WS 2 , and WSe 2 ). Specifically, characterized by the excess electrons floating on their surfaces and ultralow work functions ranging from 2.78 to 3.64 eV, 2D electrides serve as powerful electron donors. This kind of donor‐acceptor contact exhibits Ohmic behaviors and stronger interfacial coupling than vdW forces. The maximum tunneling probability can attain 100%, much higher than the 1–3% observed in common vdW 2D carbon‐based metal/MSi 2 N 4 contacts. Moreover, 2D electrides‐based contacts exhibit superior environmental stability through the bromination of their noncontact surface. This work provides valid references and insights for advancing the high‐performance of 2D electronic and photoelectronic devices.