Effect of heavy in-situ phosphorus doping on Si_1-xGe_x epitaxial growth by low-pressure chemical-vapor deposition

We have studied the effect of in-situ phosphorus doping on Si_1-xGe_x films with a high Ge fraction grown on silicon substrates at 550 °C by using low-pressure chemical-vapor deposition. In a low PHs partial pressure region, such as below 1.25×10^-3 Pa, both the phosphorus and the carrier concentrations increased with increasing PH₃ 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. Moreover, the deposition rate and the Ge fraction increased with increasing GeH₄ partial pressure while the phosphorus and carrier concentrations decreased. Si_1-xGe_x epitaxial growth is largely controlled by the surface coverage effect of phosphorus in a higher PH₃ partial pressure region, but it is controlled the Langmuir-adsorption-type kinetics in a lower pressure region.