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 intersubband transitions, i.e., bound‐to‐continuum, bound‐to‐quasibound, and bound‐ to‐bound cases. A general difference between gains measured by dark current noise and by responsivity was found for all three cases, while agreement between them was found within some ranges of bias voltages for the bound‐to‐quasibound and bound‐to‐continuum samples. The thermal noise contribution to the total white noise is explicitly modeled and discussed.