The Influence of Surfactants on the Growth of Germanium Layers on Silicon Surfaces by MBE

Abstract

ABSTRACTDeliberate introduction of a surfactant can drastically influence the growth mode of germanium on silicon. Without a surfactant germanium growth proceeds in a typical Stranski-Krastanov mode. The system is minimizing its built-in energy by undergoing strain relaxation through a clustering mechanism (islanding). In all surfactant-mediated growth processes it was possible to obtain smooth layers without island formation. The influence of different ways for introducing the surfactant layer (at the interface between substrate and growing film, in the growing film below the critical Stranski-Krastanov thickness, or on top of the grown Ge film) will be presented. Especially in surfactant-controlled solid phase epitaxy (SPE) the smooth epitaxial germanium layer was obtained by passing through an island formation stage. These islands formed below 400 °C are of different structure than the ones formed without a surfactant. Possible mechanism for the “smoothing out” of islands developed in the beginning stage of surfactant-controlled SPE will be proposed. The island formation stage can be completely suppressed by depositing the surfactant on top of the amorphous Ge layer before increasing the temperature.