A Polarization-Sensitive Self-Powered Photodetector Based on a p-WSe 2 /TaIrTe 4 /n-MoS 2 van der Waals Heterojunction.

Polarization-sensitive photodetection is highly appealing considering its great important applications. However, the inherent in-plane symmetry of a material and the single structure of a detector hinder the further development of polarization detectors with high anisotropic ratios. Herein, we design a p-WSe 2 /TaIrTe 4 /n-MoS 2 (p-Ta-n) heterojunction. As a type-II Weyl semimetal, TaIrTe 4 with an orthorhombic structure has strong in-plane asymmetry, which is confirmed by angle-resolved polarized Raman spectroscopy and second-harmonic generation. Due to the specific structure of the p-Ta-n junction with two vertical built-in electric fields, the device obtains a broadband self-powered photodetection ranging from visible (405 nm) to telecommunication wavelength (1550 nm) regions. Further, an optimized device containing 50-70 nm-thick layered TaIrTe 4 has been realized. What is more, high-resolution imaging of "T" based on the device with clear borders illustrates excellent stability of the device. Significantly, the photocurrent anisotropic ratio of the p-Ta-n detector can reach 9.1 under 635 nm light, which is more than eight times that of the best known TaIrTe 4 -based photodetector reported before. This p-Ta-n junction containing a type-II Weyl fermion semimetal can provide an effective approach toward highly polarization-sensitive and high-performance integrated broadband photodetectors.