Ultra-high-vacuum chemical vapor deposition of hetero-epitaxial Si _1-x-yGe_xC_y thin films on Si(0 0 1) with ethylene (C₂H₄) precursor as carbon source

The incorporation of substitutional carbon (C_sub) in low-temperature epitaxial Si_1-x-yGe_xC_y thin films using SiH₄, GeH₄ and C₂H₄ by ultra-high-vacuum chemical vapor deposition was investigated in this work. The Si_1-x-yGe_xC_y alloys have been grown at a temperature range from 550 to 600 °C. The C_sub content in Si _1-x-yGe_xC_y increases with increasing C ₂H₄ partial pressure under the same SiH₄ and GeH₄ condition. The addition of excessive C₂H₄ causes the degradation of Si_1-x-yGe_xC_y crystallinity, surface roughening and the suppression of Ge incorporation. The C-C double bonds in C₂H₄ were responsible for the highest percentage of C_sub, only 0.2%, incorporated in Si _0.8-yGe_0.2C_y. 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 C _sub in Si_1-x-yGe_xC_y 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 C_sub in Si_1-x-yGe_xC _y/Si heterostructure using C₂H₄ as C source.