Magnetoconductivity and potential fluctuations in semi-insulating GaAs

Low temperature measurements of the Hall effect were carried out on photoexcited electrons in EL2-rich semi-insulating GaAs before and after photoquenching of the EL2 defects. A model of conductivity in the magnetic field is proposed that takes into account essential physical aspects of the electron transport in a fluctuating electrostatic potential and describes experimental data. Both experimental results and model calculations show a decrease of the amplitude of fluctuations upon photoquenching of the EL2. However, infrared shallow donor spectroscopy measurements showed an increase of the amplitude of fluctuations upon photoquenching of the EL2. This contradiction is explained by showing that observed properties of a fluctuating pattern depend on a spatial extent of a wavefunction that probes fluctuations