SURFACTANT EFFECT OF H-ATOMS ON THE SUPPRESSION OF GE SEGREGATION IN SI OVERGROWTH ON GE(N ML)/SI(100) SUBSTRATES BY GAS-SOURCE MOLECULAR-BEAM EPITAXY

Hydrogen surfactant effect on the surface segregation of Ge atoms has been studied from layer-by-layer changes in the growth rate of Si overlayers on Ge/Si(100) substrates with Ge thicknesses of 0-6 Mb by gas source molecular beam epitaxy using Si2H6. The layer-by-layer growth rates were in-situ measured 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 that of Si/Si(100) homoepitaxial growth at substrate temperatures of 440-550 degrees C, which corresponds to the change in surface coverages of Ge atoms, The decay length of the surface concentration of Ge atoms is suppressed by an increase in Si2H6 gas pressure. The temperature dependence of the decay length has an activation energy of 1.3 eV for Si2H6 gas pressures of 5 x 10(-6) to 5 x 10(-5) Torr. These facts can be explained as an effect of H atoms existing on the surface.