Type-II Band Alignment in Bi ₂ Te ₃ /Te Nanowires Enables High Sensitivity and Ultralow Dark Current for Broadband Polarization Imaging

Type-II heterostructures enable efficient charge separation via staggered band alignment, yet their performance is fundamentally limited by an inherent sensitivity–noise trade-off that leads to high dark currents. Here, we demonstrate a Bi2Te3/Te nanowire heterojunction that overcomes this limitation through band-engineered electronic one-way transport. This mechanism simultaneously suppresses reverse dark current to 5 × 10–12 A and promotes photocarrier collection, yielding a high responsivity of 5.63 A/W at room temperature. The heterojunction dominance is confirmed by a ∼6400-fold enhanced on/off ratio (18,075–23,797, 0–1 V) over a Au/Bi2Te3 junction. Furthermore, by leveraging the anisotropic Te structure and Bi2Te3 topological states, the detector achieves a significant polarization ratio of 5.4 at 520 nm. Imaging at 0.5 mm resolution validates its broadband polarization-detection capability. This work breaks the conventional trade-off in photodetectors, providing a device that concurrently delivers ultralow dark current, high responsivity, and polarization sensitivity.