Screening effects on the degree of ionization and hole mobility for p-type Si and Ge

The degree of ionizations for Si and Ge with boron doping are calculated by taking into account the screening effect on the impurity energy level. The hole mobilities are then calculated as a function of doping concentration using the relaxation time approximation. Due to the screening effect on the impurity energy level, the degree of ionization increases over the entire temperature range. The ionized impurity scattering increases while the neutral impurity scattering decreases, and therefore the calculated mobilities for both Si and Ge agree well with the experimental data.