Electron mobility variance in the presence of an electric field

The influence of an external uniform electric field on electron mobility variance in non-degenerate n-type semiconductor is discussed. Analyzing the result of mobility fluctuation theory, according to which electron mobility variance in equilibrium semiconductor equals infinity, it is shown that in the presence of uniform electric field mobility variance becomes finite. The effect is explained in terms of the so-called electron-phonon FIT (field-induced tunnel) scattering. The results of numerical calculations of mobility variance dependence on electric field are presented for silicon and germanium. It is revealed that mobility variance decreases with the electric field increase by logarithmic law.