Abstract
We study the optical properties of GaN/AlN quantum dots (QDs) grown by molecular beam epitaxy on Si(111) substrates. Time-resolved spectroscopy of the collective emission from QD planes leads us to an appropriate determination of the QD ground state and of the on-axis internal electric field. We observe and model a nonconventional carrier recombination process. These preliminary results allow us to select the QDs that are ideal for individual studies by micro-photoluminescence. Our measurements on single QDs reveal spectral diffusion effects that we study in detail. By analyzing linear polarization, we observe properties related to the excitonic fine structure, very different from those of previously studied QDs, which we explain via a modeling accounting for exchange and anisotropy effects.