Mobility of Electrons in Germanium-Silicon Alloys

Abstract

The mobility of electrons in germanium-silicon alloys with compositions varying from 0 to 30 atomic percent silicon has been measured between 77 and 300\ifmmode^\circ\else\textdegree\fi{}K and the contribution of ionized impurity scattering has been subtracted. The resulting mobility for electrons in the conduction band with (111) symmetry was found to vary with composition as a combination of a constant term and a term varying as ${{\ensuremath{\alpha}(1\ensuremath{-}\ensuremath{\alpha})}}^{\ensuremath{-}1}$, where $\ensuremath{\alpha}$ is the mole-fraction of minority component in the alloy. In the region where either these (111) electrons or electrons in the (100) conduction band are dominating the conductivity, a subtraction of a constant mobility due to scattering by phonons leaves a mobility which varies with temperature as ${T}^{\ensuremath{-}0.7}$ to ${T}^{\ensuremath{-}0.8}$. Both of these observations are in qualitative agreement with what is to be expected on the basis of presently available theories for the scattering by disorder.