Direct Mapping of the Gate Response of a Multilayer WSe₂/MoS₂ Heterostructure with Locally Different Degrees of Charge Depletion

Understanding the interlayer charge coupling mechanism in a two-dimensional van der Waals (vdW) heterojunction is crucial for optimizing the performance of heterostructure-based (opto)­electronic devices. Here, we report mapping the gate response of a multilayer WSe₂/MoS₂ heterostructure with locally different degrees of charge depletion through mobile carrier measurements based on electrostatic force microscopy. We observed ambipolar or unipolar behavior depending on the degree of charge depletion in the heterojunction under tip gating. Interestingly, the WSe₂ on MoS₂ shows gating behavior that is more efficient than that on the SiO₂/Si substrate, which can be explained by the high dielectric environment and screening of impurities on the SiO₂ surface by the MoS₂. Furthermore, we found that the gate-induced majority carriers in the heterojunction reduce the carrier lifetime, leading to the enhanced interlayer recombination of the photogenerated carriers under illumination. Our work provides a comprehensive understanding of the interfacial phenomena at the vdW heterointerface with charge depletion.