Growth and characterization of phosphorus doped Si1−yCy alloy grown by photo- and plasma-CVD at very low temperature

The properties of Si1−yCy alloys grown on Si(001) by photo- and plasma-CVD are described. Epitaxial Si films were obtained by the addition of C2H2, CH4 or SiH2(CH3)2 to SiH4 and H2 gases at a substrate temperature of 200 °C by these two methods. Hydrogen incorporated in the epitaxial films during growth was observed to desorb on thermal annealing. The local vibration mode (607 cm−1) of C in Si was observed in the Raman spectra of films annealed at 700 °C. X-ray reciprocal lattice space mapping showed the Si1−yCy alloys to be pseudomorphic. The highest substitutional C content of 3.5 at.% was obtained in the films grown with the addition of SiH2(CH3)2. In-situ phosphorus doping was also carried out using PH3. The electron concentration of Si1−yCy films was lower than that of Si films grown at the same PH3/SiH4 ratio. However, the electron concentration was found to increase to the same level as Si films after annealing at 700 °C, to a magnitude of 5×1018 cm−3. This result implies that dopant neutralization occurred in the as-grown Si1−yCy films.