Self-Powered SnS1-xSex Alloy/Silicon Heterojunction Photodetectors with High Sensitivity in a Wide Spectral Range.

Abstract

Alloy engineering and heterostructures designing are two efficient methods to improve the photosensitivity of 2D material based photodetectors. Herein, we report the first-principle calculation about the band structure of SnS1-xSex (0 ≤ x ≤ 1) and synthesize these alloy nanosheets. Systematic measurements indicate that SnS0.25Se0.75 exhibits the highest hole mobility (0.77 cm2•V-1•s-1) and a moderate photoresponsivity (4.44 × 102 A•W-1) with fast response speed (32.1/57.5 ms) under 635 nm irradiation. Furthermore, to reduce the dark current and strengthen the light absorption, a self-driven SnS0.25Se0.75/n-Si device has been fabricated. The device achieved a preeminent photo-responsivity of 377 mA•W-1, a detectivity of ~1011 Jones and Ilight/Idark ratio of ~4.5×102. In addition, the corresponding rise/decay times are as short as 4.7/3.9 ms. Moreover, a broadband sensitivity from 635 nm to 1200 nm is obtained and the related photoswitching curves are stable and reproducibility. Noticeably, the above parameters are comparable or superior to the most of reported group IVA layered materials-based self-driven photodetectors. Last, the synergistic effects between the SnS0.25Se0.75 nanosheets and the n-Si have been discussed by the band alignment. These brilliant results will pave a new pathway for the development of next generation 2D alloy-based photoelectronic devices.