Abstract
Ordering phenomena related to the self-assembly of InAs quantum dots (QD) grown on GaAs(001) substrates are experimentally investigated on different length scales. On the shortest length-scale studied here, we examine the QD morphology and observe two types of QD shapes, i.e., pyramids and domes. Pyramids are elongated along the [1-10] directions and are bounded by {137} facets, while domes have a multi-facetted shape. By changing the growth rates, we are able to control the size and size homogeneity of freestanding QDs. QDs grown by using low growth rate are characterized by larger sizes and a narrower size distribution. The homogeneity of buried QDs is measured by photoluminescence spectroscopy and can be improved by low temperature overgrowth. The overgrowth induces the formation of nanostructures on the surface. The fabrication of self-assembled nanoholes, which are used as a template to induce short-range positioning of QDs, is also investigated. The growth of closely spaced QDs (QD molecules) containing 2–6 QDs per QD molecule is discussed. Finally, the long-range positioning of self-assembled QDs, which can be achieved by the growth on patterned substrates, is demonstrated. Lateral QD replication observed during growth of three-dimensional QD crystals is reported.
Highlights
Over the last decade semiconductor quantum dots (QDs) have attained much interest due to their electronic properties characterized by discrete atomiclike energy levels [1, 2]
This ridge, which has a width of ~100 nm and a height of ~3 nm above the flat surface, is caused by an overlap of elongated mound structures that occur during overgrowth of large QDs grown at low growth rate [23]
The step is the ordering of QD size
Summary
Over the last decade semiconductor quantum dots (QDs) have attained much interest due to their electronic properties characterized by discrete atomiclike energy levels [1, 2]. The linewidth of the peak is 29 meV, indicating a good size uniformity of the QDBMs. Figure 10c contains a summary of the PL peak position at room temperature as a function of deposited amount of InAs. The WL signal is the dominant peak up to 1.6 ML InAs deposition and the peak from the QDs in the second layer can be observed.
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