Impacts of Localized Charge Accumulation on Photocurrent Dynamics in Metal-MoS2 Contacts

Monolayer molybdenum disulfide (1L-MoS₂) has attracted a lot of attention due to its excellent electrical and optoelectronic properties. However, the challenge remains the instability of the metal-semiconductor junction, which greatly affects the performance of the drain/source contacts. Despite the promising potential offered by 1L-MoS₂ as an ultrathin two-dimensional semiconductor, its optoelectronic performance is often compromised by contact issues at the metal-semiconductor junctions. Especially, the localized charge accumulation (LCA) can cause barrier height fluctuation, which affects carrier transport and activated trap states. In this study, we use photocurrent mapping to investigate photocurrent reduction and its optoelectronic properties depending on device position. The results show a significant reduction in the photoresponsivity and photodetectivity of the LCA region compared to the channel. Moreover, the decay time of the LCA region was approximately twice as long compared to the channel, indicating the presence of deep traps leading to slow switching. This investigation highlights the significant role of photo-generated LCA region affecting metal-semiconductor junctions in degrading optoelectronics performance. It also provides a critical understanding necessary for engineering next-generation optoelectronics based on 2D semiconductors.