In-Situ RHEED Study of the Growth Mechanisms of CdSe Quantum Dots

Reflection high energy electron diffraction (RHEED) is applied to analyze the particular stages of island formation during the molecular beam epitaxy (MBE) of pseudomorphical CdSe/ZnSe on GaAs(001) using an elevated substrate temperature of TS = 400 °C. Plan-view transmission electron microscopy (TEM) images verify the existence of islands. In-situ RHEED intensity and profile analysis reveal a two-dimensional (2D) mode at growth start. Islanding begins at a CdSe coverage of 1.8 ML. After exceeding a coverage of 2.5 ML, the process of islanding is accelerated dramatically. The experimental results are interpreted as a sequence of 2D growth, Stranski-Krastanow growth-mode and ripening according to an equilibrium model predicting the surface morphology of compressively strained heterosystems.