Interwell excitons in GaAs/AlGaAs double quantum wells and their collective properties

Luminescence spectra of interwell excitons in GaAs/AlGaAs double quantum we lls with electric-field-tilted bands (n-i-n) structures were studied. In th ese structures the electron and the hole in the interwell exciton are spati ally separated between neighboring quantum wells by a narrow AlAs barrier. Under resonant excitation by circularly polarized light the luminescence li ne of the interwell excitons exhibited appreciable narrowing as their conce ntration increased and the degree of circular polarization of the photolumi nescence increased substantially. Under resonant excitation by linearly pol arized light the alignment of the interwell excitons increased as a thresho ld process with increasing optical pumping. By analyzing time-resolved spec tra and the kinetics of the photoluminescence intensity under pulsed excita tion it was established that under these conditions the rate of radiative r ecombination increases substantially. The observed effect occurs at below-c ritical temperatures and is interpreted in terms of the collective behavior of the interwell excitons. Studies of the luminescence spectra in a magnet ic field showed that the collective exciton phase is dielectric and in this phase the interwell excitons retain their individual properties. (C) 2000 MAIK "Nauka / Interperiodica".