Diffusion length and mobility in mid-wavelength InAs/InAsSb superlattice infrared detectors

In the last decade the infrared detectors with InAs/InAsSb (Gallium-free) type-II strained layer superlattice (T2SLS) absorbers became technology of interest for many imaging applications. In this work we studied dependence of minority carrier (holes), absorption coefficient and Quantum Efficiency (QE) of 5.6 µm cut-off wavelength MWIR InAs/InAsSb detectors on temperatures and applied bias. We found that the minority carrier lifetime is very long,   5.5 µs, and is temperature independent in the temperature range T = 50 – 150K. The QE without anti-reflection coating for a back side illumination increases from QE  0.3 at T = 50K to QE  0.6 at T = 180K. The minority carriers holes diffusion length, Ldh, was found from QE and absorption coefficient. The hole diffusion length, Ldh =2.4 m at T = 50 K and monotonically increases to Ldh= 7.2 m at T = 180 K. The hole mobility, calculated from diffusion length and minority carrier lifetime is h = 4.5 cm/Vs at T = 50K and increases with temperature reaching h = 7.2 cm/Vs at T = 150K.