Evaporated SexTe1‐x Thin Films with Tunable Bandgaps for Short‐Wave Infrared Photodetectors

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 SexTe1‐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 SexTe1‐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 SexTe1‐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 Se0.32Te0.68 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 Hz1/2 W−1 at 1.55 μm at room temperature. Importantly, the nature of the thermal evaporation process enables the fabrication of Se0.32Te0.68‐based 42 × 42 focal plane arrays with good pixel uniformity, demonstrating the potential of this unique material system used for infrared imaging sensor systems.