NOISE AND PHOTOCONDUCTIVE GAIN IN ALGAAS GAAS QUANTUM-WELL INTERSUBBAND INFRARED PHOTODETECTORS/

We reevaluate the current model of noise gain and photoconductive gain for AlGaAs/GaAs quantum well infrared photodetectors. An experimental study is carried out on samples covering different types of intersubb and transitions, i.e., bound-to-continuum, bound-to-quasibound, and bo und-to-bound cases. A general difference between gains measured by dar k current noise and by responsivity was found for all three cases, whi le agreement between them was found within some ranges of bias voltage s for the bound-to-quasibound and bound-to-continuum samples. The ther mal noise contribution to the total white noise is explicitly modeled and discussed.