Graphene-enhanced van der Waals contacts between three-dimensional metals and two-dimensional semiconductors

Abstract Two-dimensional (2D) semiconductors have shown great potentials for ultra-short channel field-effect transistors (FETs) in next-generation electronics. However, because of intractable surface states and interface barriers, it is challenging to realize high-quality contacts with low contact resistances for both p- and n- 2D FETs. Here, we demonstrate a graphene-enhanced van der Waals (vdWs) integration approach, which is a multi-scale (nanometer to centimeter scale) and reliable (~ 100% yield) metal transfer strategy applicable to various metals and 2D semiconductors. Scanning transmission electron microscopy imaging shows that 2D/2D/3D semiconductor/graphene/metal interfaces are atomically flat, ultraclean and defect-free. First principles calculations indicate that the sandwiched graphene monolayer can eliminate gap states induced by 3D metals in 2D semiconductors. Through this approach, we realized Schottky barrier-free contacts on both p- and n-type 2D FETs, achieving p-type MoTe2, p-type black phosphorus and n-type MoS2 FETs with on-state current densities of 404, 1520 and 761 µA µm-1, respectively, which are among the highest values reported in literatures.