Tunneling‐Induced Dark Current Suppression in Bi ₂ Se ₃ /MoTe ₂ Type‐III Heterostructures for Ultrabroadband UV‐to‐THz Detection

ABSTRACT The 2D topological insulator Bi 2 Se 3 exhibits a layered structure similar to transition metal dichalcogenides, demonstrating outstanding optoelectronic response properties. However, its high intrinsic conductivity leads to significant dark current, limiting its application in high‐performance photodetectors. This study employed a mechanical exfoliation method to fabricate Bi 2 Se 3 /MoTe 2 III‐type heterojunctions. Leveraging their unique band alignment, a potential barrier formed at the interface effectively suppressed dark current. Under a 1 V bias, the dark current was reduced to 4.9 × 10 − 9 A—five orders of magnitude lower than in single Bi 2 Se 3 devices—and achieved ultra‐wideband photodetection from 405 nm to 0.1 THz without gate voltage. Under 808 nm illumination, the device exhibits a responsivity of 0.59 A/W, a specific detection of 3.27 × 10 8 Jones, and an optical on/off ratio of 23, demonstrating excellent self‐powered characteristics. Mechanism studies indicate that light response in the 405–808 nm band is dominated by direct tunneling, while the 1550 nm and terahertz bands rely on photo‐bolometric effect. This device demonstrates application potential in multi‐wavelength single‐pixel imaging, terahertz transmission imaging, and communications, providing a viable pathway for developing high‐performance, low‐power ultra‐wideband photodetectors.