Ge/Si͑001͒ layers are grown by gas-source molecular beam epitaxy at 600°C to probe island self-ordering phenomena. We vary the Ge growth rate by a factor of 40, 1.2-47 monolayers ͑ML͒ min Ϫ1 , and adjust the Ge coverage, 5.9-8.9 ML, to produce films consisting primarily of dome-shaped Ge islands. Measurements of the radial and nearest-neighbor distributions are compared to calculated distributions for random arrangements of circular islands. At low growth rates, island formation is inhibited at small separation. At high growth rates, the angular distributions of nearest-neighbor islands show pronounced island ordering along ͗100͘ directions.
InAs self-assembled quantum dots were grown on InGaAs lattice-matched on InP by metalorganic chemical vapor deposition. The facet formation on the dot was investigated by atomic force microscopy and transmission electron microscopy. The {136}-faceted InAs dots were elongated along either [13¯0] or [3¯10] to form parallelogram-shaped islands analogous to hut cluster formation in SiGe∕Si quantum dots. Some parallelogram dots also exhibited {110} faceting, presumably on undergoing a shape transition toward dots with facets of higher symmetry.
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