Momentum Matching for 2D-3D Heterogeneous Ohmic van der Waals Contact

Construction of ohmic contact is a long-standing challenge encountered by two-dimensional (2D) device fabrication and integration. van der Waals contacts, as a new solution for 2D contact construction, can effectively eliminate issues, such as Fermi-level pining and formation of Schottky barrier. Nevertheless, current research primarily considers energy band alignment, while ignoring the transverse momentum conservation of charge carriers during the quantum tunneling across the van der Waals contacts. In this study, by comparing the IV characteristics and tunneling spectra of graphene-silicon tunneling junctions with various interfacial transverse momentum distribution, we demonstrate the importance of charge carrier momentum in constructing high-performance 2D contact. Further, by conditioning the van der Waals contacts and minimizing the momentum mismatch, we successfully enhanced the quantum tunneling current with more than three orders of magnitude and obtain ohmic-like contact. Our study provide and effective method for the construction of direction 2D-3D contact with low resistance and can potentially benefit the heterogeneous of integration of 2D materials in post-CMOS architectures.