Anomalous relaxation of dynamically localized indirect excitons in a pseudomorphic Si1−XGeX/Si double quantum well

We have studied the relaxation processes of photogenerated carriers under varied longitudinal electric fields in a pseudomorphic Si1−XGeX/Si double quantum well (QW) by measuring photoluminescence (PL) in the time-correlated single-photon-counting mode. As opposed to a monotonous decay, the temporal evolution of the PL intensities of the both wells was found to exhibit unusual modulation when the surface was positively biased. The observed anomaly is a manifestation that excitons in the buried QW dissociate under an electric field and only electrons are transferred to the near-surface well after a time lag, which can be translated into dynamic localization of electrons.