Impact ionization breakdown of n-GaAs in high magnetic fields

The influence of high magnetic field and its orientation on the impact ionization breakdown of n-type GaAs has been investigated experimentally. Hysteretic behaviour of current-voltage characteristics was observed for longitudinal magnetic field orientation to the current direction and no hysteresis was observed for transverse. The threshold voltage was much higher for transverse than for longitudinal magnetic field orientation to the current direction. The dependencies of transverse and longitudinal magnetoresistance on magnetic fields in the electric fields in pre- and post-breakdown regimes were also measured. In the pre-breakdown regime (hopping conduction) there is no great difference between the transverse and longitudinal magnetoresistance in the case when the magnetic length is much higher than the radius of an electron in the ground state on the impurity atom (low magnetic fields). In the opposite case (high magnetic fields) the transverse magnetoresistance is much higher than the longitudinal one. Such a behaviour of magnetoresistance in the pre-breakdown regime is, possibly, due to magnetic-field-induced shrinkage of the electron wavefunction. The observed great difference between the transverse and longitudinal magnetoresistance in the post-breakdown regime can be explained in terms of the Lorentz force influence on the filamentary current flow.