SURFACTANT COVERAGE AND EPITAXY OF GE ON GA-TERMINATED SI(111)

We have investigated the role of surfactant coverage and bonding for growth of Ge on Si (111). At 470-degrees-C Ge grows on Si (111)-(7 X 7) in a Stranski-Krastanov fashion. Preadsorption of 1-ML Ga at 500-degrees-C forms a Ga:Si (111)-(6.3 X 6.3) structure and alters the Ge growth mode from three-dimensional (3D) islanding to continuous film formation. However, the epitaxial layer contains defects, caused by the presence of domain boundaries of both A- and B-type material. Growth properties depend strongly on the initial Ga coverage: if a ( square-root 3 X square-root 3) surface with 1/3-mL Ga is used, a modified Stranski-Krastanov growth mode is observed, with 3D islands of a uniform predominant thickness.