Noise characteristics of quantum-well infrared photodetectors at low temperatures

In this work, we have performed high-sensitivity measurements on the dark c urrent and the noise current of infrared hot-electron transistors (IHETs) a nd their constituent quantum-well infrared photodetectors (QWIPs) at 4.2 K. We found that the dominant noise of the QWIPs in this regime is not from t he expected shot noise but from the 1/f noise and possibly a bias-independe nt noise. Part of the 1/f noise is unrelated to impurities in the barrier a nd is intrinsic to the sequential tunneling mechanism in QWIPs. By filterin g out the impurity-assisted tunneling current, the IHETs reduce the dark cu rrent and the 1/f noise, and improve the detector sensitivity and uniformit y. (C) 2000 American Institute of Physics. [S0003-6951(00)02502-X].