A flexibly switchable TaIrTe₄–WSe₂ van der Waals heterojunction photodetector with linear-polarization-dependent photosensitivity

A van der Waals heterojunction photodetector has been constructed by vertically stacking a TaIrTe₄ flake, a 2D type-II Weyl semimetal, and a WSe₂ flake, a typical isotropic 2D semiconductor. Interestingly, the device exhibits a switchable operating mode depending on the direction of the voltage bias. Specifically, under a source-drain bias of −1 V, the device operates in a photovoltaic mode, featuring rapid response rate. Its response/recovery time is down to 22.5/25.1 ms, which is approximately one order of magnitude shorter than that of a pristine WSe₂ photodetector (320/360 ms). In contrast, under a source-drain bias of +1 V, the device operates in a photoconductive mode with high photogain. The optimized responsivity reaches 9.1 A/W, and the corresponding external quantum efficiency and detectivity reach 2776% and 3.09 × 10¹² Jones, respectively. Furthermore, the effective wavelength range of the TaIrTe₄–WSe₂ device has been extended to the long-wavelength region as compared to a WSe₂ device. Beyond these, by virtue of the highly anisotropic crystal structure of TaIrTe₄, the hybrid device exhibits polarized photosensitivity. Its anisotropy ratio reaches 1.72 (1.75) under a voltage bias of +1 (−1 V). On the whole, this research work provides a paradigm for the design and implementation of 2D materials based multifunctional optoelectronic devices.