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Calculation of optimal absorber thickness in interband cascade type-II infrared InAs/GaSb superlattice photodetectors

The paper presents the performance of the interband cascade type-II infrared InAs/GaSb superlattice photodetectors. Such photodetectors are made up of multiple stages, which are connected in series using an interband tunneling heterostructure. Each stage can be divided into three regions: absorber region, relaxation region and interband tunneling region. Cascade configurations allows to achieve fast response detectors. Making the assumption of bulk-like absorbers, we show how the standard semiconductor transport and recombination equations can be extended to the case of multiplestage devices. We report on the dependence of the Johnson-noise limited detectivity on the absorber thickness for a different number of stages. This allows optimization of the detector architecture, necessary to achieve high value of the detectivity. For this purpose, we make comparison of collection efficiency in single- and multiple-stage devices. The collection efficiency rapidly increases with increasing the number of stages in multiple-absorber detector, especially in situation where the absorber material’s diffusion length is less than absorption depth. We show that the optimal value of the detectivity for different number of stages does not change significantly. The potential benefits of the cascade architecture are shown to be higher in long-term detection regime.