Achieving ultra-low Schottky barriers and tunable contact nature in boron phosphide via van der Waals integration with MXenes

Abstract Overcoming the performance bottlenecks in two-dimensional (2D) fieldeffect transistors-primarily caused by severe Fermi level pinning (FLP) and metalinduced gap states (MIGS)-requires a metallization strategy that preserves intrinsic semiconductor properties while offering controllable contact characteristics. Here, we propose a robust strategy to overcome these limitations by constructing van der Waals (vdW) heterostructures combining monolayer Boron Phosphide (BP) with fluorineterminated MXenes (M 2 CF 2 , M = Ta, W, Nb). Using density functional theory calculations, we demonstrate that the physical separation introduced by the vdW gap effectively suppresses the formation of MIGS, thereby significantly weakening the FLP effect. Consequently, the BP/M 2 CF 2 interfaces intrinsically exhibit n-type Schottky contacts with ultra-low barrier heights (0.04-0.20 eV) and high interlayer tunneling probabilities (> 3.9%). Furthermore, the contact nature exhibits exceptional tunability: reversible transitions between n-type and p-type Schottky contacts, as well as the transition into Ohmic contacts, can be realized under vertical electric fields or biaxial strain. These findings not only elucidate the microscopic mechanisms of contact barrier modulation but also quantitatively indicate low specific contact resistivities, establishing BP/MXene heterostructures as a highly feasible and promising platform for high-efficiency, reconfigurable 2D nanoelectronic devices.