Magnetoresistance effect of a current density filament in n-GaAs

Magnetoresistance of a current density filament formed by the low-temperature impurity breakdown has been measured in high-purity n-GaAs samples at 4.2 K, under magnetic fields of less than 260 mT. The resistivity of the bendable filament was measured as a function of the magnetic field intensity; it shows a good agreement with the calculated results based on ionized impurity scattering theory. For a relatively low applied electric bias, the magnetic field induces an instability of the filament, whose mechanism is discussed in detail.