Demonstration of long-wavelength infrared photodetector based on long minority carrier lifetime InAs/In0.5Ga0.5As0.5Sb0.5 type-II superlattices

This work demonstrates a significant advancement in the minority carrier lifetime of InAs/In0.5Ga0.5As0.5Sb0.5 type-II superlattices (T2SLs) designed for long-wavelength infrared (LWIR) detection. The superlattices were grown using the fractional monolayer alloy epitaxy method on GaSb substrates and subsequently integrated into nBn device architectures to suppress dark current. High crystalline quality and strong photoluminescence efficiency were confirmed. Furthermore, time-resolved microwave photoconductance decay measurements revealed a record-long minority carrier lifetime of 20.31 μs at a photoluminescence peak of 9.4 μm and a temperature of 77 K. This value surpasses those of other common LWIR T2SL materials and reached the Auger-limited lifetime for mercury cadmium telluride. The fabricated 1024 × 6 format nBn photodetectors, incorporating a 2.5 μm-thick absorber, exhibited a low dark-current density of 4.45 × 10−6 A/cm2 at 77 K. A quantum efficiency of 37.7% was achieved at 8 μm. Additionally, the detector demonstrated a noise-equivalent temperature difference below 25 mK up to 95 K, using a 7.7–10 μm bandpass filter and f/2 optics under a 300 K background. These results underscore the strong potential of InAs/In0.5Ga0.5As0.5Sb0.5 superlattices for next-generation LWIR imaging applications.