Optimal absorber thickness in interband cascade photodetectors

The paper presents the performance of the interband cascade type-II superlattice infrared photodetectors. Such photodetectors are made up of multiple stages, which are connected in series using an interband tunneling heterostructure. In this paper, we compare two different architectures of the cascade structure: equal absorber thickness in all stages and varied absorber thickness. In our calculation, in the case of equal absorber throughout the structure, we took into account electrical current gain. The selection of the first absorber thickness d(1) determines the number of possible stages N-s, at which detectivity reaches maximum value, which is especially important in case of varied absorbers thickness to meet the quantum efficiency condition (equal quantum efficiency in each stage of the device). Optimal first absorber thickness djap, is higher for equal absorbers than for matched-absorbers detectors, but maximum value of detectivity is slightly lower. We compared theoretical results with experimental ones, obtaining good agreement.