Intervalley Scattering of Hot Electrons in Germanium at Millikelvin Temperatures

A method is presented to determine the field dependence of the intervalley scattering rate for hot electrons in germanium, based on an analysis of electron straggle in a detector crystal fitted with segmented electrodes. Measurements in high-purity and in lightly doped n- and p-type crystals at millikelvin temperatures demonstrate the dominant role of impurity scattering at low field (a few V/cm), whereas phonon scattering takes precedence at higher field intensities. An analysis of the experimental data by reference to past investigations of the acoustoelectric effect in germanium strongly suggests that the impurities involved are the dopant species in the neutral state