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We presented an alternative design of type II superlattice photodiodes with the insertion of a mid-wavelength infrared M-structure AlSb∕GaSb∕InAs∕GaSb∕AlSb superlattice for the reduction of dark current. The M-structure superlattice has a larger carrier effective mass and a greater band discontinuity as compared to the standard type II superlattices at the valence band. It acts as an effective medium that weakens the diffusion and tunneling transport at the depletion region. As a result, a 10.5μm cutoff type II superlattice with 500nm M-superlattice barrier exhibited a R0A of 200Ωcm2 at 77K, approximately one order of magnitude higher than the design without the barrier. The quantum efficiency of such structures does not show dependence on either barrier thickness or applied bias.
Nguyen et al. (Mon,) studied this question.