Effects of hydrogen on the formation of SiGe/Si heterostructures
In this report, we review and discuss our results obtained on the surface segregation of Ge atoms and surfactant effects of hydrogen atoms in Si overlayer growth on Ge/Si(100) by gas-source molecular beam epitaxy (GSMBE) using GeH/sub 4/ and Si/sub 2/H/sub 6/. The layer-by-layer growth rate of the Si overlayers was observed in-situ by reflection high-energy electron diffraction (RHEED) intensity oscillation periods.
Studies on the suppression of Ge segregation during Si overgrowth on GE(n ML) / Si(100) substrates by gas-source MBE
Surfactant effects of hydrogen atoms on the Ge segregation during Si growth on Ge/Si(100) substrates by Si 2 H 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 2 H 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 2 H 6 pressures.
Is low temperature growth the solution to abrupt Si⧸Si1-xGex interface formation?
Abstract Si⧸Si1-xGex interface transients were investigated with respect to the absuptness and smoothness by using sputter depth profiling (SIMS), X-ray photoemissions (XPS), photoluminescence and transmission electron microscopy. Ge segregation was confirmed by blue-shift of luminescence energy above what is expected in a square well potential, along with SIMS measurement. Ge segregation was found to persist even at 300°C or lower. In contrast, Ge segregation was quenched by either segregant-assisted growth using Sb and Ga or solid-phase regrowth of Si cap layer; thereby a sharp Si⧸Si1-xGex interface was obtained. However, low-temperature-grown samples required an extensive anneal to restore band-edge luminescence, indicating a lack of quality of crystallinity.