Evaporated Se_xTe_1‐x Thin Films with Tunable Bandgaps for Short‐Wave Infrared Photodetectors

Abstract Semiconducting absorbers in high‐performance short‐wave infrared (SWIR) photodetectors and imaging sensor arrays are dominated by single‐crystalline germanium and III–V semiconductors. However, these materials require complex growth and device fabrication procedures. Here, thermally evaporated Se_xTe_1‐x alloy thin films with tunable bandgaps for the fabrication of high‐performance SWIR photodetectors are reported. From absorption measurements, it is shown that the bandgaps of Se_xTe_1‐x films can be tuned continuously from 0.31 eV (Te) to 1.87 eV (Se). Owing to their tunable bandgaps, the peak responsivity position and photoresponse edge of Se_xTe_1‐x film‐based photoconductors can be tuned in the SWIR regime. By using an optical cavity substrate consisting of Au/Al₂O₃ to enhance its absorption near the bandgap edge, the Se_0.32Te_0.68 film (an optical bandgap of ≈0.8 eV)‐based photoconductor exhibits a cut‐off wavelength at ≈1.7 μm and gives a responsivity of 1.5 AW⁻¹ and implied detectivity of 6.5 × 10¹⁰ cm Hz^1/2 W⁻¹ at 1.55 μm at room temperature. Importantly, the nature of the thermal evaporation process enables the fabrication of Se_0.32Te_0.68‐based 42 × 42 focal plane arrays with good pixel uniformity, demonstrating the potential of this unique material system used for infrared imaging sensor systems.