Calculation of the electron mobility for the Δ1 model of the conduction band of germanium single crystals

The concentration dependences of the charge-carrier mobility are obtained for the Δ1 model of the conduction band of n-Ge crystals on the basis of anisotropic scattering at 77 K. It is shown that the absolute-minimum inversion of the L1-Δ1 type caused by single-axis pressure on n-Ge crystals along the [100] crystallographic direction substantially decreases the charge-carrier mobility. This is explained by a decrease in the relaxation time because the effective electron masses differ only slightly in terms of different minima. For the other two cases of inversion of the L1-Δ1 absolute minimum under hydrostatic and single-axis pressure along the [110] crystallographic direction, a decrease in the electron mobility is caused mainly by an increase in the effective mass. It is shown also that it is the degree of effective-mass anisotropy that substantially affects the efficiency of charge-carrier scattering in anisotropic semiconductors in this case.