Positive and Negative Photoresponses in MoS2 Flakes Photogated by PN Junction Diode

2D materials like molybdenum disulfide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\left(\text{MoS}_{2}\right)$</tex> have shown a significant potential in photodetection due to their tunable bandgap and strong light-matter interactions. In this study, we have developed a silicon-based PN junction phototransistor integrated with few-layer <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{MoS}_{2}$</tex> to achieve tunable positive and negative photoconductivity. The device modulates photocurrent through a photo-induced voltage from the PN junction, and photocurrent measurements reveal a logarithmic dependence on light intensity.