Ultra-broadband and high response of the Bi2Te3–Si heterojunction and its application as a photodetector at room temperature in harsh working environments

Abstract

Broadband photodetection is central to various technological applications including imaging, sensing and optical communications. On account of their Dirac-like surface state, Topological insulators (TIs) are theoretically predicted to be promising candidate materials for broadband photodetection from the infrared to the terahertz. Here, we report a vertically-constructed ultra-broadband photodetector based on a TI Bi₂Te₃–Si heterostructure. The device demonstrated room-temperature photodetection from the ultraviolet (370.6 nm) to terahertz (118 μm) with good reproducibility. Under bias conditions, the visible responsivity reaches ca. 1 A W⁻¹ and the response time is better than 100 ms. As a self-powered photodetector, it exhibits extremely high photosensitivity approaching 7.5 × 10⁵ cm² W⁻¹, and decent detectivity as high as 2.5 × 10¹¹ cm Hz^1/2 W⁻¹. In addition, such a prototype device without any encapsulation suffers no obvious degradation after long-time exposure to air, high-energy UV illumination and acidic treatment. In summary, we demonstrate that TI-based heterostructures hold great promise for addressing the long lasting predicament of stable room-temperature high-performance broadband photodetectors.