Graphene/MoSi2X4: A class of van der Waals heterojunctions with unique mechanical and optical properties and controllable electrical contacts

The key solution to achieve high-performance nano-electronic devices depends on solving the contact resistance problem at the metal–semiconductor interface. Here, we construct graphene/ MoSi2X4 (X=N, P, As) van der Waals heterojunctions and investigate their mechanical, electronic, and optical properties systematically, especially focusing on their electrical contact features. It is found that such intrinsic heterojunctions hold a low Schottky barrier height (SBH) and better electrical contact behavior. Particularly, the more ideal electrical contact can be realized by vertical strain and electric field regulations. For example, vertical strain can cause a transition between n-type and p-type Schottky contacts, even leading to a switching from p-type Schottky to p-type Ohmic contacts for graphene/MoSi2X4 (X=P, As) vdWHs, and an applied electric field can make a conversion from Schottky contacts (n-, p-type) to well-defined Ohmic contacts (n-, p-type) for all heterojunctions. Furthermore, physical regulations can induce high-concentration carrier doping in graphene, up to 1013 cm−2, under external electric field, which provides new possibility to design graphene/MoSi2X4-based high-gain transistors. And also shown is that these heterojunctions also possess a reasonable Poisson ratio and high stiffness features, robustly enough to withstand geometrical deformation and mechanical damage, indicating that they are suitable as electrode and nano-device materials.