2D Free‐Standing GeS_1−xSe_x with Composition‐Tunable Bandgap for Tailored Polarimetric Optoelectronics

Abstract Germanium‐based monochalcogenides (i.e., GeS and GeSe) with desirable properties are promising candidates for the development of next‐generation optoelectronic devices. However, they are still stuck with challenges, such as relatively fixed electronic band structure, unconfigurable optoelectronic characteristics, and difficulty in achieving free‐standing growth. Herein, it is demonstrated that two‐dimensional (2D) free‐standing GeS_1−xSe_x (0 ≤ x ≤ 1) nanoplates can be grown by low‐pressure rapid physical vapor deposition (LPRPVD), fulfilling a continuously composition‐tunable optical bandgap and electronic band structure. By leveraging the synergistic effect of composition‐dependent modulation and free‐standing growth, GeS_1−xSe_x‐based optoelectronic devices exhibit significantly configurable hole mobility from 6.22 × 10⁻⁴ to 1.24 cm²V⁻¹s⁻¹ and tunable responsivity from 8.6 to 311 A W⁻¹ (635 nm), as x varies from 0 to 1. Furthermore, the polarimetric sensitivity can be tailored from 4.3 (GeS_0.29Se_0.71) to 1.8 (GeSe) benefiting from alloy engineering. Finally, the tailored imaging capability is also demonstrated to show the application potential of GeS_1−xSe_x alloy nanoplates. This work broadens the functionality of conventional binary materials and motivates the development of tailored polarimetric optoelectronic devices.