Ge segregation in SiGe/Si heterostructures and its dependence on deposition technique and growth atmosphere

Ge segregation at SiGe/Si heterointerfaces has been studied for films deposited by atmospheric pressure chemical vapor deposition (APCVD), ultrahigh vacuum CVD (UHV/CVD) and molecular beam epitaxy (MBE). Profiles were taken by secondary-ion-mass-spectroscopy (SIMS) of samples grown with these techniques at the same growth temperatures and Ge concentrations. The MBE grown profiles are dominated by segregation of Ge into the Si top layer in the temperature range from 450 to 800 °C. SiGe/Si interfaces deposited by UHV/CVD at elevated temperatures are smeared, but at 515 °C and below the interfaces are abrupt within the resolution of the SIMS. Heterostructures grown by APCVD show abrupt interfaces and no indication of Ge segregation in the investigated temperature range from 600 to 800 °C. Surface passivation by hydrogen appears to be responsible for the suppression of the Ge segregation in CVD processes.