Localised exciton transitions in high-quality GaAs/AlGaAs quantum wells

We investigate the origin of optical interband transitions in high-quality GaAs/AlGaAs quantum wells. Using a novel microphotoluminescence technique based on the excitation and collection through a standard single-mode fibre, we are able to detect very narrow emission lines. Furthermore a model describing the localisation at quantum well interfaces is developed, which gives more insight into the nature of the states involved in optical emission.