Two-Dimensional MoS ₂ /SnS ₂ Isotype van der Waals Heterojunction Photodetectors with Thickness-Dependent Gate-Tunable Rectification Reversal

Two-dimensional (2D) materials exhibit outstanding optoelectronic properties, and van der Waals (vdW) heterostructures assembled from them possess unique electronic characteristics. With rational design, these structures enable the realization of multifunctional and high-performance electronic and optoelectronic devices. In this work, an all-dry transfer technique was employed to fabricate MoS2/SnS2 n–n isotype vdW heterojunction photodetectors with inverse thickness configurations on both SiO2 and h-BN substrates. From an electrical perspective, we report for the first time the gate-tunable rectification reversal behavior in MoS2/SnS2 isotype vdW heterojunctions, exhibiting a high rectification ratio of up to 1.45 × 104. This rectification polarity reversal shows a pronounced dependence on the thicknesses of the constituent materials. Moreover, the devices demonstrate an impressive field-effect on/off ratio reaching 106. Regarding optoelectronic performance, the SiO2/MoS2/SnS2 device─dominated by a photovoltaic mechanism─achieves a dark current as low as 690 fA under negative gate bias, with a high responsivity of 7.08 A W–1 and a specific detectivity of up to 1.097 × 1012 Jones. In contrast, the h-BN/MoS2/SnS2 device─governed primarily by a photoconductive mechanism─achieves an even higher responsivity of 11.9 A W–1, a light-to-dark current ratio exceeding 105, and significantly reduced response times enabled by gate modulation. This dual-response mechanism offers a versatile platform for balancing ultralow noise and high sensitivity in photodetection. Overall, this study presents a novel strategy for exploiting vdW heterostructures of 2D materials in multifunctional and high-performance applications, including photodetectors, diodes, transistors, programmable rectifiers, and ternary logic devices.