Wide-Spectrum Polarization Detection Based on Lattice-Induced Prepared Heterojunctions

Polarization photodetection has attracted much attention as a promising method to get more information from the target objects, and in this field, two-dimensional (2D) materials with a low-symmetric structure show great potential for their ability to distinguish light with different polarization direction. However, limited by the intrinsic crystal structure and forbidden bandwidth of such materials, there are hindrances in optimizing polarization photodetection performance, such as improving the anisotropic current ratio as well as expanding the detection spectral range. Even though low-symmetric materials have been stacked through mechanical transfer as a possible solution, the varying relative angles between different materials and the pollution at the interface induced during the transfer process still have negative effects on the photodetection performance of these heterojunctions. In order to solve the mentioned problems, a strategy to form highly low-symmetry GeSe₂–GeSe heterojunctions by selenization of single GeSe crystals has been proposed, for which the b-axis direction of GeSe₂ and the armchair direction of GeSe are spontaneously in parallel. The synthesized heterojunctions with type-II energy band arrangement can reach an anisotropic current ratio up to 3.5 (at 808 nm) and exhibit a higher absorption compared to single GeSe. This work presents a scheme for preparing low-symmetry heterojunctions by in situ transformation, which suggests a potential approach for optimizing linearly polarized photodetectors based on the designed heterojunctions’ growth.