Engineering 2D Van der Waals Electrode via MBE-Grown Weyl Semimetal 1T'-WTe2 for Enhanced Photodetection in InSe.

Achieving low contact resistance in advanced quantum electronic devices remains a critical challenge. With the growing demand for faster and energy-efficient devices, 2D contact engineering offers a promising solution. Beyond graphene, 1T'-WTe2 has attracted attention for its excellent electrical transport, quantum phenomena, and Weyl semimetallic properties. Here, the direct wafer-scale growth of 1T'-WTe2 via molecular beam epitaxy (MBE) and its use as a 2D contact for layered materials, such as InSe, are demonstrated. The 1T'-WTe2/InSe interface exhibits a barrier height nearly half that of conventional metal contacts, and its contact resistance is reduced by a factor of 21, effectively suppressing Fermi-level pinning and enabling efficient electron injection. InSe/1T'-WTe2 photodetectors show broad photoresponsivity (0.14-217.58 A W-1) under NIR to DUV illumination with fast rise/fall times of 42/126 ms, compared to lower responsivity (8.65 × 10-4-3.64 A W-1) and slower response (150/144 ms) for InSe/Ti-Au devices. The 1T'-WTe2/InSe devices thus exhibit ≈60 × higher responsivity and ≈4 × faster response than conventional metal contacts. These results establish MBE-grown 1T'-WTe2 as an effective 2D electrode, enhancing photodetection performance while simplifying device architecture, making it a strong candidate for next-generation nanoelectronic and optoelectronic devices.