Interfacial Synergy in a Band‐Aligned Low‐Dimensional Heterojunction Toward Broadband Photodetection

ABSTRACT Monolithic integration of sensing, imaging, and communication from visible to terahertz bands on a single chip remains challenging as efficient detection across such disparate energies demands stringent, often incompatible material properties. However, conventional semiconductors suffer from intrinsic bandgap limitations or require cryogenic cooling, while existing low‐dimensional heterojunctions often struggle to synergize multiband response kinetics and suppress interfacial carrier recombination. Here, we demonstrate a band‐aligned low‐dimensional heterojunction based on Ta ₂ NiSe ₅ and Sb ₂ Te ₃ that leverages interfacial synergy to unify complementary photoresponse pathways, thereby enabling ultrabroadband and low‐noise photodetection spanning across visible to terahertz regimes. The device delivers stable responsivities of up to 0.19 A·W ⁻¹ in the visible–near‐infrared regime, while antenna‐enhanced coupling extends detection into the terahertz range with microsecond transients, 10 kHz bandwidth, and a minimum noise‐equivalent power of 26 pW·Hz ^−1/2 . A built‐in potential of 115 meV, originating from the Type‐II band alignment, plays a dual role by ensuring highly efficient carrier separation in the short‐wavelength band and driving a strong photothermoelectric effect in the terahertz regime. The synergistic interfacial response allows further implementation of reconfigurable logic operations and dual‐channel ASCII data transmission using visible and terahertz signals as independent carriers, highlighting its potential for anti‐jamming communication and multifunctional photonic systems.