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. ©1995 American Institute of Physics.