Electron Mobility Fluctuations in Polar Semiconductors

Some problems related to electron mobility fluctuations in polar semiconductors are discussed. The theory of electron-polar optical phonon field-induced tunnel scattering has been developed. Based on the obtained relation for the scattering rate in the case of weak fields, it was shown that in the presence of an electric field, the electron mobility variance takes on finite values, in contrast to the absence of a field, when it diverges. Using GaAs as an example, the dependence of the electron mobility variance on the electric field is computed, which is given by the decreasing function according to the logarithmic law. The frequency dependence of the spectral density of mobility fluctuations in polar semiconductors has the same qualitative form as in non-polar semiconductors: in a fairly wide frequency range it is described by the 1/f law, and in the presence of an electric field in the low-frequency region a saturation region appears. The temperature dependence of the electron mobility noise parameter in GaAs is computed, which qualitatively and quantitatively agrees with some experimental data on the temperature dependence of the Hooge parameter of low-frequency current noise in n-GaAs.