Dark Current Characteristic of p-i-n and nBn MWIR InAs/GaSb Superlattice Infrared Detectors

The theoretical dark current model of InAs/GaSb type II superlattice (T2SL) p-i-n and nBn photodetectors is presented. The nBn structure was designed to suppress generation-recombination (G-R), surface leakage and tunnel currents. 8 band k·p model including the conduction and valence band mixing was applied to calculate the band structure and optical transition of InAs/GaSb T2SL. Theoretical calculations are performed for different doping level of p-i-n and nBn detectors. For p-i-n detector, dark current was studied for different p-contact layer doping and different absorber layer doping. For nBn detector, different contact doping concentration and absorb doping concentration was studied. At low temperature, dark current of p-i-n detector was dominant by generation-recombination and tunnel current, nBn structure can inhibit tunnel and generation-recombination current. At high temperature, the dark current of p-i-n detector and nBn detector have the same order of magnitude and are both dominated by diffusion current. Quantum efficiency and resistance-area product of p-i-n and nBn detectors were also calculated at 120 K, quantum efficiency of p-i-n detector is a bit larger than nBn detector, but dark current and resistance area product of nBn detector are better.