Low-frequency noise gain and photocurrent gain in quantum well infrared photodetectors

We present a theory of the low-frequency noise gain gn and photocurrent gain gp in quantum well infrared photodetectors (QWIPs). Expressions for gn and gp in terms of QW capture probability pc and number of QWs N are obtained. These expressions are valid for any number of QWs N>=1 and capture probability 01) to 1 (for pc-->0). QWIP is well described by a conventional photoconductor theory in the case of low capture probability pc-->1, which corresponds to practical QWIPs. The assumptions of the model are discussed in detail, and a comparison with previously published results is made.