Achieving Ohmic and High-Tunneling-Probability Contacts in 2D Semiconductors via Hydrogen-Bond-Mediated Interfacial Coupling.

Developing high-performance electronics with two-dimensional (2D) semiconductors is often hindered by high contact resistance at metal/semiconductor interfaces, which arises from the Schottky barrier for carrier injection and tunneling barrier for carrier transport. Conventional contact engineering faces a fundamental compromise: strong interfacial coupling induces Fermi-level pinning (FLP), while weak van der Waals interactions mitigate FLP but introduces a large tunneling barrier. Here, we overcome this compromise by employing MXene electrodes on Janus MGeSiN4 (M = Mo, W) semiconductors and modulating the interfacial interaction strength. Through selective surface termination of MXenes, Schottky, n-type Ohmic, or p-type Ohmic contacts can be achieved. Notably, medium-strength interfacial coupling driven by hydrogen bonding in OH-terminated MXene (OH-MXene)/MGeSiN4 contacts enables simultaneous Ohmic behavior and high tunneling probability. Specifically, the tunneling probability of OH-MXene contacts ranges from 37.91% to 61.92%, with the maximum for Ti3C2(OH)2/WGeSiN4 on the Si-N side, significantly higher than F/O-terminated MXene contacts (1.87% - 6.19%). Quantum transport simulations confirm superior current transport and charge injection efficiency in OH-MXene/MGeSiN4 devices. Furthermore, the Sure Independence Screening and Sparsifying Operator method identifies key descriptors governing both Schottky and tunneling barriers. Our results provide an efficient strategy for designing high-performance contacts in 2D electronic devices.