Photo and dark current noise in self-assembled quantum dot infrared photodetectors

Current noise is investigated in InAs/GaAs self-assembled quantum dot infrared photodetectors in the dark and under irradiation at T=4.2K. At low temperature, the noise is consistent with a mechanism of fluctuations driven by the electric field, related to field- and photon-assisted tunneling rather than trapping–detrapping of charge carriers from the quantum dots. In particular, a strong noise suppression effect determines the decrease of the fluctuation intensity as the voltage increases in the negative differential photoconductivity region of the I–V characteristics. The noise suppression mechanism acts in the dark and under irradiation. The noise intensity decreases consistently with the occurrence of the nonlinear differential photoconductivity effect.