Studies on the suppression of Ge segregation during Si overgrowth on [formula omitted] substrates by gas-source MBE

Abstract

Surfactant effects of hydrogen atoms on the Ge segregation during Si growth on Ge Si(100) substrates by Si 2H 6-source molecular beam epitaxy have been studied. The layer-by-layer growth rates were examined in-situ by reflection high energy electron diffraction (RHEED) intensity oscillation periods. The growth rate of Si overlayers decreases exponentially with increasing Si thickness and eventually approaches to that of Si Si(100) homoepitaxial growth at substrate temperatures of 440–550°C, which corresponds to the change in surface coverage of Ge atoms. The decay length of the surface concentration of Ge atoms is suppressed by an increase in Si 2H 6 gas pressure. These facts can be explained as an effect of H atoms existing on the growing surface. Furthermore, the atomic mixing phenomenon in the initial stage of growth is observed, which is related with the strain of Ge layers. The addition of excess hydrogen atoms during Si growth leads to a further reduction of the decay length under the appropriate growth condition and to the island growth at higher temperatures and for lower Si 2H 6 pressures.