Lowering Contact Resistance by Quasi-Covalent Bonding in a Sr₂N-WSe₂ Donor–Acceptor Heterostructure

High contact resistance of a metal–semiconductor junction is one of the main limitations in the development of next-generation integrated circuits on transition-metal dichalcogenides. Here, a new Sr2N/WSe2 heterostructure with a lower tunneling barrier and a stronger orbital overlap was designed. Our first-principles calculations indicated that its theoretical specific tunneling resistivity (2.82 × 10–11 Ω cm2) can be reduced by 2 orders of magnitude compared to that of a typical van der Waals heterostructure (1.60 × 10–9 Ω cm2 for Sb(01–12)-MoS2). The strong orbital interaction and metallization of the contact region are responsible for such a significant improvement in performance. Both gate-voltage-induced external electric field and substrate-induced strain can diminish the Schottky barrier and finally realize Ohmic contact in the Sr2N/WSe2 heterostructure. Our method of reducing contact resistance is technically compatible with current large-scale integrated circuit technology and makes it reach quantum limitations in various heterostructures.