With increasing temperature, phonon concentration increases and causes increased scattering. Thus lattice scattering lowers the carrier mobility more and more at higher temperature. Theoretical calculations reveal that the mobility in non-polar semiconductors, such as silicon and germanium, is dominated by acoustic phonon interaction. The resulting mobility is expected to be proportional to T , while the mobility due to optical phonon scattering only is expected to be proportional to T . Experimentally, values of the temperature dependence of the mobility in Si, Ge and GaAs are listed in table.