Extrinsic Origin of Persistent Photoconductivity in Monolayer MoS2 Field Effect Transistors

Recent discoveries of the photoresponse of molybdenum disulfide (MoS₂) have shown the considerable potential of these two-dimensional transition metal dichalcogenides for optoelectronic applications. Among the various types of photoresponses of MoS₂, persistent photoconductivity (PPC) at different levels has been reported. However, a detailed study of the PPC effect and its mechanism in MoS₂ is still not available, despite the importance of this effect on the photoresponse of the material. Here, we present a systematic study of the PPC effect in monolayer MoS₂ and conclude that the effect can be attributed to random localized potential fluctuations in the devices. Notably, the potential fluctuations originate from extrinsic sources based on the substrate effect of the PPC. Moreover, we point out a correlation between the PPC effect in MoS₂ and the percolation transport behavior of MoS₂. We demonstrate a unique and efficient means of controlling the PPC effect in monolayer MoS₂, which may offer novel functionalities for MoS₂-based optoelectronic applications in the future.