Photoconductive gain and generation-recombination noise in quantum well infrared photodetectors

Photocurrent and excess current noise in a quantum well infrared photodetector are considered using a drift-diffusion model of charge carrier transport. The effect of quantum well recharge under the influence of the nonuniform generated charge carriers is addressed. The recharging effect drastically changes the dependency of both photoconductive gain and excess current noise gain upon detector parameters. We have found that for uniform generation, both gains coincide. For nonuniform generation, noise gain is essentially different from photoconductive gain. This distinction is of the order of 100% for the real device parameters. The existing discrepancy in formulae for photoconductive gain and excess current noise derived in different models, which implicitly assumed drift transport of electrons, is cleared up.