Tunable ambipolar polarization-sensitive photodetectors based on high anisotropy ReSe$_{2}$

Atomically-thin 2D layered transition metal dichalcogenides (TMDs) have been extensively studied recently because of their intriguing physical properties and promising applications in nanoelectronic devices. Among them, ReSe$_{2\, }$is a material that exhibits a stable distorted 1T phase and strong in-plane anisotropy. Here, the anisotropic nature of ReSe$_{2}$ is revealed by Raman scattering under linearly polarized excitations. Utilizing high-quality ReSe$_{2}$ nanosheets, we are able to build top-gate ReSe$_{2}$ field-effect transistors which show an excellent on/off current ratio exceeding 10$^{7}$ and a well-developed current saturation at room temperature. Importantly, the successful synthesis of ReSe$_{2}$ directly onto hexagonal boron nitride substrates has effectively improved the electron motility over 100 times and the hole mobility over 50 times at low temperatures. Remarkably, the ReSe$_{2\, }$based photodetectors show a polarization-sensitive photo-responsivity due to the intrinsic linear dichroism originated from high in-plane optical anisotropy. With a back gate the linear dichroism photodetection can be unambiguously tuned both in the electron and hole regime. The appealing physical properties of ReSe$_{2}$ demonstrated in this study identify it as an emerging candidate for electronic and optoelectronic applications.