Scattering Anisotropies inn-Type Silicon

Measurements have been made of magnetoresistance effects in several relatively pure samples of $n$-type silicon for the purpose of obtaining information on scattering anisotropies. The results indicate that the ratios of relaxation times parallel and perpendicular to a constant-energy-spheroid axis in the six-valley conduction band of silicon are $\frac{{\tau }_{\mathrm{II}}}{{\tau }_{\perp }}\approx \frac{2}{3}$ for acoustic-mode intravalley lattice scattering and $\frac{{\tau }_{\mathrm{II}}}{{\tau }_{\perp }}>1\mathrm{}$ for ionized-impurity scattering. Intervalley lattice scattering, important at higher temperatures, is isotropic.