Hole diffusion length and mobility of a long wavelength infrared InAs/InAsSb type-II superlattice nBn design

We demonstrated high-performance 8.9 μm cutoff wavelength nBn InAs/InAsSb type-II strained-layer superlattice (T2SL). These detectors exhibit a long minority carrier (hole) lifetime of 1.2 μs at 80 K, high quantum efficiency of 40% for back-side illuminated devices without antireflection coating, and low dark current density of 4.6 × 10−6 A/cm2 at 80 K. We measured absorption, minority carrier (hole) lifetime, quantum efficiency, and spectral response as a function of the temperature and applied bias. We investigated the temperature dependence of the hole diffusion length and mobility and found that their values increase with temperature from 1.3 μm and 6.5 cm2/Vs at 30 K to 6.5 μm and 36 cm2/Vs at T = 90 K. We compared the measured diffusion length and mobility of holes in long-wavelength infrared (LWIR) T2SL with these parameters of a high-performance mid-wavelength infrared (MWIR) T2SL. Unexpectedly, hole mobility in LWIR T2SL was found to be higher than in MWIR that is contrary to the theoretical predictions.