Evaporated Se_xTe_1-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 Se(x)Te(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(x)Te(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(x)Te(1-)(x)film-based photoconductors can be tuned in the SWIR regime. By using an optical cavity substrate consisting of Au/Al(2)O(3)to enhance its absorption near the bandgap edge, the Se(0.32)Te(0.68)film (an optical bandgap of approximate to 0.8 eV)-based photoconductor exhibits a cut-off wavelength at approximate to 1.7 mu m and gives a responsivity of 1.5 AW(-1)and implied detectivity of 6.5 x 10(10)cm Hz(1/2)W(-1)at 1.55 mu m at room temperature. Importantly, the nature of the thermal evaporation process enables the fabrication of Se0.32Te0.68-based 42 x 42 focal plane arrays with good pixel uniformity, demonstrating the potential of this unique material system used for infrared imaging sensor systems.