SURFACTANT-STABILIZED STRAINED GE CONES ON SI(001)

The formation of circular cone-shaped Ge islands (12 degrees cones) has been observed for the growth of eight monolayers of Ge on Si(001) at 700 degrees C using Sb as a surfactant. The Ge cones are strained and grow pseudomorphically, adopting the Si lattice constant. They have a tilt angle of 12 degrees and are composed of [117]-, [105]-type, and all intermediate facets. The island-size distribution is peaked around a typical size of similar to 300-400 Angstrom, which results from a formation process under equilibrium conditions for diffusion of the Ge atoms. Growth at lower temperatures down to 300 degrees C with Sb as a surfactant results in epitaxial but very rough Ge films which show a high degree of disorder.