For chamber base pressure ≊5×10−4mbar in a rapid thermal processing chemical vapor deposition system, a 900 °C H2prebake for 60 s results in relatively high defect densities in the GexSi1−xepitaxial layer due to surface damage caused by the H2prebake. We have demonstrated that a very low thermal budgetinsitupreclean (800 °C/15 s) can reduce the defect densities. In addition, the use of a Si buffer layer grown at 1000 °C for 60 s prior to the GexSi1−xgrowth is capable of significantly reducing defect densities.