  We reported a new result of the neutral impurity scattering of holes that has
impact on the charge drift mobility in high purity p-type germanium crystals at
77 Kelvin. The charge carrier concentration, mobility and resistivity are
measured by Hall Effect system at 77 Kelvin. We investigated the contribution
to the total charge drift mobility from ionized impurity scattering, lattice
scattering, and neutral impurity scattering with the best theoretical models
and experimental data. Several samples with measured Hall mobility from the
grown crystals are used for this investigation. With the measured Hall mobility
and ionized impurity concentration as well as the theoretical models, we
calculated the neutral impurity concentration by the Matthiessen's rule. As a
result, the distributions of the neutral impurity concentrations with respect
to the radius of the crystals are obtained. Consequently, we demonstrated that
neutral impurity scattering is a significant contribution to the charge drift
mobility, which has dependence on the concentration of neutral impurities in a
given germanium crystal.
