Space charge buildup in quantum-well infrared photodetectors leading to low-power nonlinear photoresponse

Space charge buildup in quantum-well infrared photodetectors (QWIPs) is shown to be the main reason for the low-power nonlinear photoresponse of the QWIPs. We present a model that takes into account the space charge distribution across the quantum wells and derive a simple expression for the intensity dependent responsivity of the QWIP. A comparison of our model with a set of intensity dependent responsivity measurements performed on a 50-period QWIP shows a very good agreement with our model as long as the QWIP is far from saturation.