Current noise suppression in quantum well infrared photodetectors at low bias voltages

摘要

The power spectrum of current noise in Quantum Well Infrared Photodetectors (QWIP) is calculated considering the smoothing effect of electron Coulomb interaction on the noise to account for the noise suppression observed in QWIP's at low external bias. Actually, when the external voltage is low, it has been shown that the potential at the collector is inverted with respect to the emitter. Such potential distribution gives rise to a longer electron transit through the interelectrodic region. As a result, each electron emitted at the cathode, during the longer transit time through the device, reduces the transmission probability of the emitter barrier and thus increases the waiting time for a subsequent electron emission, which results in a low frequency current noise reduced with respect to the equivalent vacuum tube shot noise 2eI, in agreement with the experimental findings.