Impact ionization breakdown of n-GaAs in high magnetic fields

The influence of high magnetic field and its orientation on the impact ioni zation breakdown of n-type GaAs has been investigated experimentally Hyster etic behaviour of current-voltage characteristics was observed for longitud inal magnetic field orientation to the current direction and no hysteresis was observed for transverse. The threshold voltage was much higher for tran sverse than for longitudinal magnetic field orientation to the current dire ction. The dependencies of transverse and longitudinal magnetoresistance an magnet ic fields in the electric fields in pre- and post-breakdown regimes were al so measured. In the pre-breakdown regime (hopping conduction) there is no great differen ce between the transverse and longitudinal magnetoresistance in the case wh en 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 c ase (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 magne toresistance in the post-breakdown regime can be explained in terms of the Lorentz farce influence on the filamentary current flow.