Hydrogen-bonding enables two-dimensional metal/semiconductor tunable contacts approaching the quantum limit and the modified Schottky-Mott limit simultaneously

Achieving efficient electrical contacts in two-dimensional (2D) semiconductors is increasingly critical with the continuous scaling down of transistors. van der Waals (vdW) contacts with weak Fermi-level pinning are still hindered by the additional contact resistance due to weak interlayer coupling. Here, based on first-principles, we propose to exploit hydrogen-bonding interactions to intrinsically overcome the inherent vdW gap. Various metal/semiconductor heterojunctions with hydroxyl-terminated MXenes as the metal electrode demonstrate clean Ohmic contacts with ultralow contact resistance approaching the quantum limit via strong hydrogen-bonding of O-HMIDLINE HORIZONTAL ELLIPSISX (X = N, O, S, Se, etc.) at the interface. Hydrogen-bonding contacts are further shown to be an advantageous approach to achieve near-perfect N-type contacts for emerging 2D nitride, oxide, halide, and chalcogenide semiconductors that can simultaneously approach the modified Schottky-Mott limit. We finally discuss the general design concepts for hydrogen-bonding contacts, demonstrating their potential to go beyond vdW contacts in achieving ideal electrical contacts in 2D semiconductors. This first-principles study proposes utilising hydrogen-bonding to overcome the van der Waals gap and demonstrates Ohmic contacts approaching the quantum limit and the modified Schottky-Mott limit in various two-dimensional semiconductor systems.