Current noise in quantum well infrared photodetectors: effect of electron Coulomb interaction

摘要

The power spectrum of current noise in quantum well infrared photodetectors (QWIPs) is calculated, considering the smoothing effect of long-range Coulomb interaction on the noise in order to account for the shot-noise suppression observed in QWIPs at low external biases. When the external voltage is low, the random emission of each electron from the cathode, due to the potential distribution through the device, reduces the transmission probability of the triangular emitter barrier during its transit time, giving a feedback effect on the current fluctuations. From a statistical point of view, in each interaction volume the time interval between two consecutive electron injections cannot be therefore described by Poisson statistics, which are valid for fully independent electrons. The work will be thus addressed to deducing a statistics accounting for the correlation between electrons during their transit through the device. Finally, it will be shown that at low frequencies the power spectral density of noise, calculated using such statistics, is reduced by a factor of up to 0.5, depending on the operating conditions of the device. [References: 5]