LOCALIZATION EFFECTS CAUSED BY THE REMOTE DONORS IN MODULATION-DOPED QUANTUM WELLS

We have developed a theoretical model to determine the size and scale of potential fluctuations 2 eta created in the 2D electron gas in the QW by the random distribution of ionized donors modeled as a 2D sheet. We show that for E//F//E greater than eta all electrons are localized at low temperature, while for E//F//E less than eta there are both localized and free electrons. This behavior manifests itself in experimental results of mobility measurements using persistent photoconductivity which exhibit a mobility edge. Photoluminescence results where the oscillator strength for the localized electrons is suppressed compared with free electrons recombining with the few photo-excited localized holes also support this theory since the fluctuations separate the localized electrons and holes in real space.