Electric field redistribution under IR radiation in quantum well infrared photodetectors as deduced from current noise measurements at low temperature and bias

Abstract

Current noise has been investigated in AlGaAs/GaAs quantum well infrared photodetectors (QWIPs), having nominally the same design except the number of wells N. The experiments have been carried out in the dark and under infrared (IR) radiation in a wide range of currents and temperatures. We have found that the current noise scales as the inverse of the number of wells N in the dark condition. In the presence of IR radiation, the noise exhibits strong deviations from the simple 1/ N behavior. These effects are still more evident when the photocurrent noise is measured at low biases and temperatures. Nonlinear effects in the QWIPs operation at high IR power, related to the potential redistribution in the interelectrodic region, are probably responsible for such anomalies. This conclusion is consistent with results of the steady-state responsivity obtained in the QWIPs in the same experimental conditions.