Boron-controlled solid phase epitaxy of germanium on silicon: A new nonsegregating surfactant

Abstract

10-nm-thick germanium layers have been grown on Si(100) with boron as a surfactant with three different growth procedures, and investigated with reflection high-energy electron diffraction, transmission electron microscopy, and secondary ion mass spectroscopy. We obtained smooth and completely closed epitaxial germanium layers only by depositing the boron on top of the amorphous germanium layer followed by a post-annealing step. The surface energy anisotropy of the germanium will be affected by the presence of boron in this equilibrium process. The islanding observed in all other growth processes can be understood by taking into account that boron is a typical nonsegregating material in Ge below 600 °C and a surfactant acts mainly due to its presence in the growing front.