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

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 mu m. 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 similar to 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. (C) 2016 Elsevier Ltd. All rights reserved.