Influence of composition fluctuations in Al(Ga)As barriers on the exciton localization in thin GaAs quantum wells

The localization of excitons in thin GaAs/Al(Ga)As quantum wells has been investigated by micro- and time-resolved photoluminescence (FL) spectroscopy. A fine-structured line shape in micro-PL is found not only for exciton recombination in the GaAs well but also, very similarly, for the Al(Ga)As barrier luminescence. By means of time-resolved measurements we show that the observed barrier luminescence probes selectively a barrier region close to the top interface of the quantum well. Our results directly reveal the essential contribution of Al(Ga)As composition fluctuations to the excition localization in GaAs/Al(Ga)As quantum wells.