Negative Photoresponses in MoS2 Flakes Photogated by p-n Junction Diode

Negative photoresponses in photodetectors can find important applications like image AI and image edge detection. In this Letter, we develop a few-layer MoS2 phototransistor photogated by a silicon-based N+P junction. Negative photovoltage will be generated on the open-circuit N+P junction by grounding the p-type substrate. The negative photovoltage modulates the conductance of the n-type MoS2 flake, creating negative photoconductance in the MoS2 channel. The light-intensity dependent photoresponses are characterized at cryogenic temperatures. The experimental results can be well fitted with the established device theory.