We demonstrate nearly-spherical, strain-free, self-assembled Ge quantum dots
(QDs) fully encapsulated by AlAs, grown on (100) GaAs by molecular beam epitaxy
(MBE). The QDs were formed without a wetting layer using a high temperature,
in-situ anneal. Subsequent AlAs overgrowth was free from threading dislocations
and anti-phase domains. The straddling band alignment for Ge in AlAs promises
strong and tunable confinement for both electrons and holes. The reflection
high-energy electron diffraction (RHEED) pattern changed from 2x3 to 2x5 with
anneal, which can be explained by surface reconstructions based on the
electron-counting model.Comment: 14 pages, 5 figures, submitted to Applied Physics Letter
