Polarization-State-Driven Band Engineering Enabling Mobility Bidirectional Modulation and Photodetection Enhancement in SnS ₂ /In ₂ Se ₃ Heterostructures

van der Waals (vdW) heterostructure photodetectors constructed from two-dimensional (2D) semiconductors have driven progress from passive photodetection to actively tunable and multifunctional optoelectronic devices. In particular, 2D ferroelectric semiconductors may enhance photodetection by switchable, nonvolatile polarization fields. However, the influence of electric-field-induced band structure modulation in ferroelectric materials on the electrical and optoelectronic performance of heterostructure devices remains insufficiently explored. In this work, we fabricate a SnS 2 /α-In 2 Se 3 heterostructure photodetector that exhibits bias-voltage-controlled, ferroelectric state-dependent, bidirectional modulation of carrier mobility and shows an exceptionally high photoresponsivity of 52.24 A·W –1 under an optical power density of 35.6 μW·cm –2 . These exceptional features of the SnS 2 /In 2 Se 3 photodetector mainly arise from enhanced carrier separation driven by the modified built-in interfacial electric field and the polarization fields of In 2 Se 3 . Besides, due to the presence of the built-in electric field, the SnS 2 /In 2 Se 3 photodetector exhibits a rise time that is 14.53 and 2.06 times faster than that of SnS 2 - and In 2 Se 3 -only devices. Therefore, we elucidate a unique interfacial modulation mechanism in 2D ferroelectric/semiconductor systems, providing a new strategy for the design of tunable, energy-efficient, high-sensitivity photodetectors and their imaging arrays.