Magnetoresistance inn-Type Germanium at Low Temperatures

Magnetoresistance was studied for $n$-type single-crystal germanium of 4×${10}^{15}$ effective donors/${\mathrm{cm}}^3$. The effective anisotropy parameter $K$ was found to decrease from ∼20 at 300°K to ∼6 at 20°K. Values close to 20 were again obtained at 7°K and 4.2°K. By introduction of compensating acceptors with heat treatment, it was shown directly that the decrease of $K$ was due to anisotropic scattering by ionized impurities, and the anisotropy was investigated by using different degrees of compensation. Below 7°K, the scattering is determined by neutral impurities, and the high value of $K$ indicates that the scattering is isotropic.