Hydrogen-bonded MXene ohmic contacts: overcoming Schottky and tunneling barriers for quantum-limit 2D MoS2 electronics

Abstract

Metal–semiconductor (MS) contacts often suffer from high Schottky barriers, poor carrier injection, and low tunneling probability. While van der Waals (vdW) materials can reduce Schottky barriers, their weak interactions and large interfacial gaps introduce additional tunneling barriers, increasing impedance. To address this, we propose MS heterojunctions with hydrogen bonding at the interface to lower tunneling impedance. Using hydroxyl-saturated MXenes in contact with monolayer MoS₂, we achieve ohmic contacts and enhanced carrier injection. Hydrogen bonding induces a strong electric dipole, reducing both the height and width of the tunneling barrier. Tunneling probabilities (P_TB) scale linearly with interfacial spacing and binding strength. Among 24 M₃X₂T₂ (X = C/N, T = OH/NH)/MoS₂ heterojunctions, Ta₃N₂(OH)₂/MoS₂ exhibits the highest P_TB (45.24%) and the lowest tunneling impedance (0.033 × 10⁻⁹ Ω cm²). This approach offers a promising strategy for achieving ideal electrical contacts in low-dimensional devices.