Electric Field Influence on n-GaAs Magnetoresistance in Impurity Conduction

The effect of electric fields on the magnetoresistance of intermediately doped crystals (4 × 10¹⁵ ≦ ≦ n_e ≦ 3 × 10¹⁶ cm⁻³) of n-type epitaxial gallium arsenide a t T = 4.2 K is studied. It is established that negative magnetoresistance is observed only in weak electric fields. Positive magnetoresistance is observed in an electric field higher than the impurity breakdown field. A transition from negative magnetoresistance to positive magnetoresistance is found to occur in an electric field less than the breakdown field. A model is suggested to explain magnetoresistance changes in electric fields, which takes into account the decrease of the negative component of magnetoresistance due to a decrease in the concentration of magnetic centres and the increase of the positive component due to the appearance of nonequilibrium carriers in the conduction band.