Suppressing the vdW Gap-Induced Tunneling Barrier by Constructing Interfacial Covalent Bonds in 2D Metal–Semiconductor Contacts

Abstract

2D metal and semiconductor materials provide a promising solution to realize Ohmic contacts by suppressing the strong Fermi level pinning (FLP) effect due to without dangling bonds. However, the 2D metal-semiconductor Van der Waals (vdW) interfaces induce an inevitable tunnel barrier, significantly restraining the injection of charge carriers into the conduction channel. Herein, by replacing the vdW bond with the covalent bond in interfaces, the Ohmic and tunneling-barrier-inhibition contacts are realized simultaneously based on the 2D XSi₂N₄ (X = Cr, Hf, Mo, Ti, V, Zr) semiconductor and the 2D Mxene metal family. Taking 60 2D Mxene-XSi₂N₄ contacts as examples, although the vdW-type contacts exhibit Ohmic contacts, the tunneling probability (P_TB) can be as low as 0.4%, while the P_TB can increase to 88.09% by removing the Mxene terminations at the adjacent interface to form the covalent bond. The weak FLP and Ohmic contacts are retained at covalent bond interfaces since the outlying Si─N sublayer protects the band-edge electronic states of XSi₂N₄ semiconductors. This work provides a straightforward strategy for advancing high-performance and energy-efficient 2D electronic nanodevices.