Achieving Fermi-Level Depinning and Ideal Metal Contact in β-Ga2O3 Devices via MXene Integration.

The Fermi-level pinning (FLP) effect critically compromises the performance of semiconductor devices. Here, we propose a transformative paradigm, namely, two-dimensional (2D) metal/three-dimensional semiconductor van der Waals (vdW) contacts, and demonstrate it with Ti3C2Tx/β-Ga2O3 interfaces. We first elucidated the mechanism governing the work function of Ti3C2Tx and subsequently established a library of Ti3C2Tx metals with work functions spanning from 1.50 to 6.52 eV. A series of Ti3C2Tx/β-Ga2O3 vdW heterostructures were then constructed, in which the interfacial vdW barrier effectively blocks the metal-induced gap states, thereby enabling Fermi-level depinning with a high pinning factor of S = 0.60 and a continuous tuning of the Schottky barrier height from 0.15 to 3.12 eV. Furthermore, by intentionally engineering the interfacial bonding from vdW forces to covalent bonds, we demonstrate both widely tunable Schottky barriers and ideal ohmic contacts within the same system. This study provides a theoretical foundation for advanced semiconductor devices.