Emerging vertically stacked n-Bi₂Te₂Se/p-Bi₂Te₃ topological insulator heterojunction for high-performance self-powered photosensor

An investigation into the properties and performance of a novel fabricated topological insulator (TI) material, namely n-Bi₂Te₂Se/p-Bi₂Te₃-based vertical heterojunction fabricated by thermal evaporation technique, as an efficient photosensor. The chosen material combination leverages the inherent properties of n-Bi₂Te₂Se and p-Bi₂Te₃ to form a heterostructure (HS) that shows excellent charge transport characteristics and facilitates, generation and separation of photoexcited carriers. A self-powered heterojunction sensor was fabricated, exhibiting an ultra-high photoresponsivity of 429.95 A/W, a high detectivity of 3.57 × 10¹² Jones, and an ultralow Noise equivalent power (NEP) of 1.95 × 10⁻¹⁴ WHz^−1/2 obtained at 661.24 µW/cm² under 1300 nm illumination. We have also systematically estimated the different properties of topological insulator (TIs) materials and their heterostructures by ab-initio method based on density functional theory (DFT). The Electronic properties of Bi₂Te₃ and Bi₂Te₂Se thin films (1 QL) and Bi₂Te₂Se/Bi₂Te₃ HS are estimated. The band gap of Bi₂Te₂Se/Bi₂Te₃ HS was observed to be 0.11 eV. The optical properties such as dielectric response of these TI materials and their HS are investigated using DFT with independent particle approximation (IPA). These Bi₂Te₂Se, Bi₂Te₃ TI materials and their HS are shown to be broadband light absorption, with their highest absorption occurring at 3.07, 2.9, and 3.06 eV.