Current Oscillations and High-Field Domains in Photoexcited High-Resistivity GaAs

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Abstract
Current oscillations (10 kHz∼102kHz) due to the periodic generation of a moving high-field domain have been observed in high-resistivity GaAs (∼3×103ohm-cm in the dark) under illumination at room temperature. It has been found that threshold field for the oscillation decreases with increasing illumination level and lies in the range from 650 V/cm to 2100 V/cm. Properties of the high-field domain have been investigated by a light probe and a contact probe technique. The domain velocity is 103cm/sec∼104cm/sec. Width and field of the domain are of the order of 10-2cm and 104V/cm, respectively. By shifting a light spot position along the specimen to change the distance that the domain transits, the oscillation frequency can be varied continuously. The origin of the oscillations can be explained with field-enhanced electron trapping at deep levels.