Gated <i>PN</i> Junction in Ambipolar MoS ₂ for Superior Self‐Powered Photodetection

Abstract Self‐powered photodetectors (SPPDs) have attracted significant attention as a key component of future technologies that require ultra‐low power consumption, such as mobile edge devices. Molybdenum disulfide (MoS 2 ), a representative van der Waals semiconductor, has emerged as a promising SPPD candidate due to its superior optoelectronic properties compared to conventional bulk materials. However, forming a pn photodiode with MoS 2 is challenging due to its strong n ‐type characteristics and the presence of nonideal metal–semiconductor interfaces. Here, high‐performance MoS 2 SPPDs are reported, exhibiting a photoresponsivity exceeding 21 A W −1 , a detectivity as high as 3.7 × 10 13 Jones, and a rectification ratio over 10 7 , without requiring complex heterostructures, chemical doping, or multiple gates. To realize an ideal MoS 2 pn junction, Pt and graphite asymmetric bottom electrodes are introduced into a partial‐gate architecture, where hole injection is notably facilitated. The clearly developed ambipolar behavior of MoS 2 with Pt bottom contacts allows for the estimation of band modulation efficiency and corresponding built‐in potential, close to the MoS 2 bandgap, across the high‐quality pn junction. The self‐powered photodetection phenomenon is electrically tunable, as demonstrated through extensive electrical and optoelectrical characterization, including scanning photocurrent microscopy, combined with theoretical analysis.