Localized electric-field-enhanced low-light detection by a 2D SnS visible-light photodetector*

Abstract

Due to their excellent carrier mobility, high absorption coefficient and narrow band gap, most 2D IVA metal chalcogenide semiconductors (GIVMCs, metal=Ge, Sn, Pb; chalcogen=S, Se) are regarded as promising candidates for realizing high-performance photodetectors. We synthesized high-quality two-dimensional (2D) tin sulfide (SnS) nanosheets by the method of physical vapor deposition (PVD) and fabricated an 2D SnS visible photodetector. The photodetector shows a high photoresponsivity of 161 A·W^-1 and possesses an external quantum efficiency of 4.45×10⁴%, as well as a detectivity of 1.15×10⁹ Jones under 450 nm blue light illumination. Moreover, under an illumination of an optical density weak to 2 mW·cm^-2, the responsivity of the device is higher than that of a stronger optical density. We suggest that the photogating effect in the 2D SnS photodetector is mainly responsible for the weak-light responsivity. Defects and impurities in the 2D SnS can trap carriers and form localized electric fields, which can delay the recombination process of the electron-hole pairs and prolong the carrier lifetime, and thus improve the weak-light responsivity. This work provides design strategies for weak light detection of 2D material photodetectors.