Enhancement of the Hall mobility in undoped GaAs with low carrier concentration by light excitation

We report the investigation of the steady-state Hall mobility behavior upon extrinsic light excitation in n-type liquid-encapsulated Czochralski GaAs crystals. The carrier concentration of the samples measured in the dark ranged from 10(8) to 3x10(11) cm(-3). The Hall mobility demonstrated a pronounced minimum in the concentration region 10(9)-10(11) cm(-3). In samples of this region a significant increase of the Hall mobility from greater than or equal to 1460 to 6300-7800 cm(2) V s could be induced by light, in some cases without an increase of the measured carrier concentration. Such behavior was explained by reduction of the mesoscopic nonuniformities related to the cellular structure of dislocations by the carriers generated from defect levels in the band gap. (C) 1997 American Institute of Physics.