Temperature dependence of the size distribution function of InAs quantum dots on GaAs(001)

We present a detailed atomic-force-microscopy study of the effect of annealing on InAs/GaAs(001) quantum dots grown by molecular-beam epitaxy. Samples were grown at a low growth rate at 500 °C with an InAs coverage slightly greater than critical thickness and subsequently annealed at several temperatures. We find that immediately quenched samples exhibit a bimodal size distribution with a high density of small dots (<50 nm3) while annealing at temperatures greater than 420 °C leads to a unimodal size distribution. This result indicates a coarsening process governing the evolution of the island size distribution function which is limited by the attachment-detachment of the adatoms at the island boundary. At higher temperatures one cannot ascribe a single rate-determining step for coarsening because of the increased role of adatom diffusion. However, for long annealing times at 500 °C the island size distribution is strongly affected by In desorption.