Investigations of quantum efficiency in type-II InAs/GaSb very long wavelength infrared superlattice detectors

Abstract In this paper, we have investigated the quantum efficiency ( QE ) of InAs/GaSb T2SL very long wavelength Infrared (VLWIR) photodetectors with 50% cutoff of 12.7 μm. Due to the small depletion width and similar absorption coefficient in the T2SL material system, the minority-carrier diffusion length was determined as the key element to improve the QE of VLWIR T2SL photodetectors. The minority-carrier diffusion length was estimated by a comparison of the experimental data with the Hovel model. Our result suggest that the short hole diffusion length ( L h  ∼ 520 nm) and the large its ratio to the width of this region ( x n /L h ) are considered against the photo-excited carrier collection in the T2SL photodetectors. In addition, the influence of surface recombination velocity ( S h ) on the QE of the T2SL photodetectors is also studied. The change of QE with S h is not so significant due to the relatively low absorption coefficient and short hole diffusion length in our photodetector.