Photoconductive gain and generation-recombination noise in quantum-well photodetectors biased to strong electric field

The influence of the nonuniform photogeneration on the electric-field distribution is considered for quantum-well photodetectors under drift velocity saturation. We found that spatial nonuniformity of photogenerated electrons due to attenuation of the infrared flux induces strong electric-field domains. The electric-field domains formation is accompanied by degradation of the signal-to-noise ratio. We obtained that domain structures undergo realignment at certain threshold voltage as a result of feedback influence of the quantum well recharging on the photogeneration rates which in turn cause the additional electric-field redistribution. The realignment manifests itself in a steplike change of photoconductive gain and quantum efficiency of photoabsorption at threshold bias voltage and is followed by considerable increase of generation-recombination noise.