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Ge/Si(100) islands were found to coarsen during in situ annealing at growth temperature. Islands were grown by molecular-beam epitaxy of pure Ge and annealed at substrate temperatures of T = 450, 550, 600, and 650°C, with Ge coverages of 6.5, 8.0, and 9.5 monolayers. Three coarsening mechanisms operate in this temperature range: wetting-layer consumption, conventional Ostwald ripening, and Si interdiffusion. For samples grown and annealed at T = 450°C, consumption of a metastably thick wetting layer causes rapid initial coarsening. Slower coarsening at longer annealing times occurs by conventional Ostwald ripening. Coarsening of samples grown and annealed at T = 550°C occurs via a combination of Si interdiffusion and conventional Ostwald ripening. For samples grown and annealed at T ⩾ 600°C, Ostwald ripening of SiGe alloy clusters appears to be the dominant coarsening mechanism. [ABSTRACT FROM AUTHOR]

Annealing molecular beam epitaxy grown Ge/Si(100) islands spontaneously forms quantum dot molecules and rings. Quantum dot molecules (QDM) are close-packed arrays of several SiGe alloy hut clusters arranged with rectangular or circular symmetry. Rings are 3D structures with a depressed center. Both of these structures are related to island ensemble coarsening. Si interdiffusion into the perimeter of nominally pure Ge dome clusters forms a Si-rich annulus surrounding a Ge rich core. This lower melting point core diffuses away during coarsening of the island ensemble leaving behind the QDM. Large ring structures are formed by rapid coarsening of large, dislocated clusters during high temperature anneals. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]