Ultra-high-vacuum chemical vapor deposition of hetero-epitaxial Si1−x−yGexCy thin films on Si(0 0 1) with ethylene (C2H4) precursor as carbon source

The incorporation of substitutional carbon (Csub) in low-temperature epitaxial Si1−x−yGexCy thin films using SiH4, GeH4 and C2H4 by ultra-high-vacuum chemical vapor deposition was investigated in this work. The Si1−x−yGexCy alloys have been grown at a temperature range from 550 to 600 °C. The Csub content in Si1−x−yGexCy increases with increasing C2H4 partial pressure under the same SiH4 and GeH4 condition. The addition of excessive C2H4 causes the degradation of Si1−x−yGexCy crystallinity, surface roughening and the suppression of Ge incorporation. The C-C double bonds in C2H4 were responsible for the highest percentage of Csub, only 0.2%, incorporated in Si0.8−yGe0.2Cy. The Ge, B and C concentration were determined by secondary ion mass spectroscopy (SIMS). The total C atoms incorporation efficiency is ∼0.05. The maximum concentration of Csub in Si1−x−yGexCy increases with the decrease of Ge content. In the ambient of hydride-based CVD at low-growth pressure and temperature, the presence of GeH4 would impede the incorporation of Csub in Si1−x−yGexCy/Si heterostructure using C2H4 as C source.