GROWTH AND STRUCTURAL CHARACTERIZATION OF MOLECULAR-BEAM EPITAXIAL ERBIUM-DOPED GAAS

Elemental erbium from a thermal effusion cell has been used to dope gallium arsenide grown by molecular beam epitaxy with erbium concentrations of 4 x 10(16) to 2 x 10(20) cm-3. No incorporation dependence on substrate temperature was observed over the range 540-630-degrees-C. Transmission electron microscopy has revealed a solubility limit of erbium in GaAs of approximately 7 x 10(17) cm-3 at 580-degrees-C. Above this concentration, erbium is incorporated primarily as near spherical micro-precipitates which possess a cubic (rocksalt) structure consistent with their chemical composition being ErAs. The precipitate size during the molecular beam epitaxial growth is dependent primarily on the substrate temperature and can be controlled in the 10-20 angstrom range. Larger precipitates produce misfit dislocations and are no longer spherical. The mechanism represents a simple method for the fabrication of quantum dots distributed uniformly in three dimensions.