Selective Charge Injection via Topological van der Waals Contacts for Barrier-Free p-Type TMD Transistors

The continued miniaturization of electronic and optoelectronic devices places stringent demands on contact engineering for 2D semiconductors, particularly for p-type materials, where achieving low-resistance contacts remains a critical challenge. While van der Waals (vdW) contacts offer a promising route for next-generation electronics, the impact of microscopic interfacial phenomena on device performance remains insufficiently understood. Here, how selective charge injection is revealed to be governed by key interfacial parameters between WTe₂, a topological vdW contact, and both Se- and S-based transition metal dichalcogenide (TMD) channel materials. Through device measurements and first-principles simulations, it is shown that WTe₂ forms an exceptional vdW contact with p-type MoSe₂, exhibiting an ultralow Schottky barrier height (≈7 meV), low contact resistance (≈0.47 kΩ µm), and high carrier mobility (373 cm² V⁻¹ s⁻¹). This selective charge injection is attributed to a larger interlayer distance in WTe₂/Se-based TMDs, which suppresses orbital overlap and preserves interface quality. These microscopic descriptors serve as essential design principles for future 2D electronic and optoelectronic systems.