Fig. 2

Underlying mechanism of photodetection in the detector. a Back-gate dependence of drain current under dark and different irradiance intensities, the orange dash arrow shows the V _T shift towards negative gate voltage with increasing illumination intensity due to the photo-gating effect. b V _T shift (∆V _T) as a function of light power on the detector, the blue line is the non-linear fitting at relatively high light power regime and the dark yellow line shows a slope as high as 618 V pW⁻¹ at low light power. c Responsivity of the device as a function of back gate at V _DS of 10 V and under varying irradiance, demonstrating the increased responsivity and more sensitive detection capability by applying large-positive gate voltage. d Energy band diagram of the out-of-plane PN junction at the interface (top panel) and the N-MoS₂ transport channel (bottom panel) with applied bias under V _G < V _T. e The same with d but under V _G > V _T showing the more efficient charge separation and recirculation due to the larger built-in field and negligible contact barrier. f Temporal response of the device at different back-gate voltage and V _DS of 10 V and under irradiance of 31.7 µW cm⁻²