Electron mobility measurement in n-GaAs at low-temperature impurity breakdown

Using a combination of the standard Hall technique and the photoluminescenc e imaging of galvanomagentic transport, free-electron density and mobility have been measured in the regime of filamentary current flow after the elec tric breakdown of n-GaAs at the temperature of liquid helium. The data show good agreement with those acquired by the geometrical magnetoresistance ef fect and by the optical Hall angle measurement. By comparing the mobilities obtained by independent techniques, arguments have been found indicating s ignificant neutral impurity scattering in the post-breakdown regime. In the pre-breakdown regime variable range hopping has been concluded as the domi nant transport mechanism.