T2SL*

Mid-infrared (Mid-IR) detectors are essential for applications in earth science and atmospheric sensing, security and defense, health and medicine, and even communication.  For mid-IR imaging applications, large arrays of mid-IR detectors are used to recreate thermal images. Such systems are known as focal plane arrays (FPAs). Mid-IR detection in semiconductor-based photodetectors is highly dependent on the collection efficiency of photo-excited charge carriers and thus directly affected by recombination processes. These recombination mechanisms become more prominent in patterned structures such as focal plane arrays where surface recombination is no longer negligible in comparison to bulk recombination mechanisms. As a result, the minority carrier lifetime is a key component for efficient detection; particularly in focal plane arrays where pixels’ Signal-to-Noise ratio is significantly affected by surface recombination. We characterize the minority carrier lifetime of mid-wave infrared type-II superlattice (T2SL) structures utilizing time-resolved microwave reflectance (TMR) in both bulk and patterned T2SL samples. To elucidate the impact of surface recombination, we evaluate with various patterned samples through dimensional scaling to alter surface to volume characteristics. We use scanning electron microscopy (SEM) to analyze the sidewall profiles of patterned surfaces and correlate surface dimensions to changes in minority carrier lifetime.