Investigations on the formation kinetics of CdSe quantum dots

Abstract

High- resolution TEM investigations reveal that CdSe quantum dot samples are often characterised by the existence of two different types of islands, which form a bimodal size distribution. Analysing the density distribution function of the two dominating size classes of islands, we show that islands of an average size of about 16 nm (type B islands) are clearly correlated with a phase transition via a Stranski–Krastanow growth process. The smaller clusters with a size of less than 10 nm (type A islands) are formed during the growth of the wetting layer, bevor the critical wetting layer thickness is reached. The stability range for the formation of dislocation-free SK islands was experimentally determined. We discuss gain measurements and stimulated emission of vertically stacked CdSe–ZnSe quantum dot structures which were grown on tilted GaAs substrates.