Mid-infrared photothermoelectric detector using topological insulator BiSb thin film

We demonstrate a mid-infrared (MIR) photothermoelectric (PTE) detector based on a Bi 90 Sb 10 thin film, a topological insulator with strong MIR absorption and a high Seebeck coefficient. BiSb films were deposited by magnetron sputtering, a scalable and cost-effective method, on both sapphire and flexible Kapton substrates. The PTE response was systematically evaluated for various device geometries. A maximum voltage of 27 µV was obtained for a 16 mm × 0.25 mm × 80 nm film on sapphire. A 3 × 3 array of 4 mm × 0.25 mm elements was demonstrated. Finally, we demonstrated a large PTE response of 170 µV with improved detectivity D * of 1.1⋅10 5 cmHz/W for a BiSb-based PTE device on a Kapton flexible substrate. These results highlight the potential of sputtered BiSb thin films for large-area MIR detector arrays with low fabrication cost.