Noise gain vs. capture probability in single quantum well infrared photodetectors at low bias voltages

A model of low frequency current noise SI(0) is developed for single quantum well (QW) infrared photodetectors. A retarding mechanism, between subsequent electron injections in the QW structure, might dominate under a given threshold voltage value corresponding to the inversion of the electric field at the collector barrier. By considering this effect in terms of correlation between subsequent stochastic elementary events, the expressions of SI(0) and of noise gain gn, defined as SI(0)/4eI, are deduced. In particular, it is found that, when the applied voltage V→0 and the capture probability pc→1, the noise gain gn reaches the minimum value gn=1/4.