[en] We have studied epitaxial crystal growth of Si_1-xGe_x films on silicon substrates at 550 .deg. C by low pressure chemical vapor deposition. In a low PH₃ partial pressure region such as below 1.25x10^-3 Pa, both the phosphorus and carrier concentrations increased with increasing PH₃ partial pressure, but the deposition rate and the Ge fraction remained constant. In a higher PH₃ partial pressure region, the deposition rate, the phosphorus concentration, and the carrier concentration decreased, while the Ge fraction increased. These suggest that high surface coverage of phosphorus suppresses both SiH₄ and GeH₄ adsorption/reactions on the surfaces, and its suppression effect on SiH₄ is actually much stronger than on GeH₄. In particular, epitaxial crystal growth is largely controlled by surface coverage effect of phosphorus in a higher PH₃ partial pressure region