We studied the evolution of holed nanostructures by gallium droplet epitaxy on a GaAs surface. A linear relationship between the height and diameter of outer rings from holed nanostructures was found. Further, an empirical rule to predict the ratio of height to outer ring diameter for Ga and In holed nanostructures was established. This rule provides deeper insights to quantum rings formation from droplet materials.
We studied the multilayering effects of InGaAs quantum dots (QDs) on GaAs(731), a surface lying inside of the stereographic triangle. The surfaces after stacking 16 InGaAs layers were characterized with highly non-uniformity of QD spatial distribution. The bunched step regions driven by strain accumulation are decorated by QDs, therefore GaAs(731) becomes a good candidate substrate for the growth of QD clusters. The unique optical properties of the QD clusters are revealed by photoluminescence measurements. By adjusting the coverage of InGaAs, a bamboo-like nanostructured surface was observed and the quantum dots aligned up in clusters to separate the "bamboo" into sections.
The effects of spacer thickness on lateral alignment and density of InGaAs quantum dots on GaAs(311)B substrates is investigated. As the thickness of the spacer layers is increased, the two-dimensional lateral ordering previously demonstrated on GaAs(311)B is replaced by the one-dimensional dot chains normally observed on GaAs(100). Additionally, the dot density is found to increase proportionally with spacer thickness. The transition of lateral alignment regimes results from two processes competing to dominate the growth mechanism: the elastic anisotropy of the matrix and the characteristics of surface diffusion.
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