InAs/GaAs quantum dot formation studied by magneto-photoluminescence spectroscopy

InAs/GaAs quantum dots (QDs) formation was studied by photoluminescence (PL) in magnetic fields up to 50 tesla. In the set of samples investigated, the amount of InAs deposited on [100] and [311]B oriented GaAs was varied from 1.4 to 1.9 monolayers in steps of 0.1 monolayer. On the [100] plane, the large PL linewidths reveal the presence of QDs for an InAs coverage of as little as 1.4 ML. However, up to 1.5 ML an asymmetrical PL-line is observed together with a large diamagnetic energy shift between 0 T and 50 T. In field, the different contributions to the PL-line shift differently, separating their centers of mass. This reveals that the PL- line consists of two peaks: a broad one, characteristic of QD luminescence and a narrow one that we attribute to the wetting layer (WL). The changeover to a symmetric PL, line and the sudden drop in diamagnetic shift at 1.6 ML indicate that the luminescence is dominated by the QDs from 1.6 ML on. In this regime, the charges are well confined inside the QDs. From this point, the decrease in localisation with further increase in InAs coverage leads to a slight increase in diamagnetic shift.