High-Responsivity Near-Infrared-II Photodetector Based on 1T-WS₂/Si Heterojunction

Here, we propose and demonstrate a 1T-WS2/Si heterojunction for the high-responsivity near-infrared-II (NIR-II) photodetector by pulsed laser deposition method. The device exhibits an unique NIR photoresponse with a high signal-to-noise ratio of $10^{{2}}\sim 10^{{3}}$ between visible and NIR light through optimization of the 1T-WS2 film thickness. Notably, the responsivities up to 1.02 A/W@1310 nm and ~0.97 A/W@1550 nm at bias voltage of −1 V are achieved, which are superior to those of the previous transition metal chalcogenides/Si heterojunctions but also are comparable to some commercial InGaAs photodetectors in NIR-II region. Moreover, the presented heterojunction can be utilized to realize more accurate heart rate monitoring in photoplethysmogram system.