Influence of thin GaAs and AlAs cap layers on the structural properties of InAs quantum dots grown by molecular beam epitaxy

Self-organised InAs quantum dots (QDs) are used as optical gain material in long wavelength lasers on GaAs. The measured QD height and density are often used as figures of merits, and great efforts have been made to maximise these two parameters to extend the wavelength coverage. In this work, we investigate the influence of initial GaAs and AlAs cap layers on the structural properties of InAs QDs. The study clearly shows that capping of InAs QDs causes a strong modification of not only the QD shape and height but also the QD density.