High-responsivity near-infrared-II photodetector based on 1T-WS₂/Si heterojunction

Here, we propose and demonstrate a 1T-WS ₂ /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 ~10 ³ between visible and NIR light through optimization of the 1T-WS ₂ 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.