  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.
