Ultra-broadband response and extreme low-light detection with a MoS2/SnS2 vertical heterostructure photodetector.

Low-light detection technology is of strategic significance in military reconnaissance and deep space exploration. However, existing photodetectors often struggle to achieve both broadband response and ultra-low-light detection capabilities simultaneously. In this work, a MoS₂/SnS₂ vertical heterostructure photodetector was fabricated using an in-situ two-step chemical vapor deposition (CVD) method. The device successfully realized a broadband coverage ranging from ultraviolet to infrared regions (250-1064 nm) and demonstrated high-sensitivity photodetection of low-light signals. Under illumination at the intensity of 0.0008 mW/cm² and the wavelength of 520 nm, the device showed a responsivity of 6.89 A/W. This enhancement is attributed to the type-II band alignment of the MoS₂/SnS₂ heterojunction, which promotes efficient charge separation and suppresses carrier recombination. Under 30 mW/cm² illumination at 385 nm, the response time was reduced to 0.082/0.074 s (rise/fall time). At the wavelengths of 385 and 520 nm, the limit of detection reached as low as 0.0008 mW/cm², indicating a low-light detection capability one order of magnitude superior to that of commercial black-Si detectors. Furthermore, based on the measured noise characteristics and responsivity, we estimate a minimum detectable radiance of 6.11×10⁻¹³ W/(cm² sr μm) at 450 nm when normalized to a standard detector area of 4.91 mm². This theoretical value approaches the radiance level of nighttime atmospheric glow, indicating the potential of our heterostructure for ultra-sensitive photodetection applications after appropriate scaling.