Investigations on the formation kinetics of CdSe quantum dots

High-resolution TEM investigations reveal that CdSe quantum dot samples are often characterised by the existence of two different types of islands, wh ich form a bimodal size distribution. Analysing the density distribution fu nction 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 w ith 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 thicknes s is reached. The stability range for the formation of dislocation-free SK islands was experimentally determined. We discuss gain measurements and sti mulated emission of vertically stacked CdSe-ZnSe quantum dot structures whi ch were grown on tilted GaAs substrates. (C) 2000 Elsevier Science B.V. All rights reserved.