Crystalline-to-amorphous transition in chemical vapor deposition of pseudomorphic Si_1-x-yGe_xC_y films

Pseudomorphic SiGeC films have been grown on (100) Si by atmospheric pressure chemical vapor deposition at 600 and 700 °C using SiH₂Cl₂, GeH₄, and C₂H₄ precursors. Films with C concentrations of up to 2.5 at. % were entirely pseudomorphic and a 120-nm-thick Si_66.5Ge₃₁C_2.5 film had 90% substitutional carbon. With increasing C incorporation due to increased ethylene flow, a layered structure was formed consisting of an amorphous film overlaying a buried pseudomorphic film. The crystalline-to-amorphous transition was initiated by the accumulation of C on the epitaxial growth surface. This deteriorated surface resulted in the formation of stacking faults along {111} planes and subsequent amorphization. Defect formation and amorphization could be prevented by periodically growing a thin Si epilayer.