Influence of the wetting-layer growth kinetics on the size and shape of Ge self-assembled quantum dots on Si(001)

Abstract

The growth temperature of the wetting layer is used as the key variable in the study of a series of Ge self-assembled quantum dots on Si(001) substrates. A relaxed SiGe buffer layer is used for most of the samples as a means of maintaining the density of Ge dots. Ge dots are in the shapes of pyramids, domes, and superdomes, similar to those reported in the literature. A significant difference in the fraction of pyramids is observed between samples with wetting layers grown at low (280 °C) and high (650 °C) temperatures. This difference is in turn dependent on the total amount of Ge deposited or equivalently, the average size of dots. These observations point to the presence of Si during the initial stage of Ge dot formation and that the fraction of pyramids as well as the critical size for the transition from pyramids to domes are influenced by the presence of Si.