Deformation Potential Theory forn-Type Ge

The deformation potential theory has been re-examined for electrons in Ge to take into account the ellipsoidal nature of the energy surfaces, and the effect of shear wave scattering. The coupling between shears and the conduction band energy minima is calculated from Smith's piezoresistance data under the assumption that any changes in mobility due to strain may be neglected. The scattering by shears, which is the dominant mechanism, is strongly anisotropic and cannot be described by a simple relaxation time. We have shown that the distribution function for electrical conductivity has a tensor dependence on the orientation of the electric field. The mobility is calculated assuming several values of $E_{1c}$, the shift of the conduction band edge with dilation. The calculated values of the mobility are approximately $3\times {10}^7{T}^{-\frac{3}{2}}$ ${\mathrm{cm}}^2$/v sec. Methods of accounting for discrepancies between the experimental and theoretical values of the mobility and its temperature dependence are discussed.