Slow domains and negative resistance via the enhanced capture of transferred electrons in n-type GaAs

Abstract

Slow domains in oxygen doped n-type GaAs with photoexcited conductivities ranging from 10-8 to 10-4 ( Omega CM)-1 have been investigated in the temperature range 100 to 200 K. It is proposed that the origin of these domains is the transferred electron effect with enhanced trapping from the (100) valley. The low threshold voltages are attributed to high resistance layers near the alloyed contacts of width about 10 mu m in low resistivity samples and about 100 mu m in high resistivity samples. A theoretical model is proposed for the domain incubation which invokes a sub nl product behaviour of the cathode layer and compared with experimental results of incubation time against applied field and the variation of threshold field with sample length. The trap-modified drift velocity against field curve has been calculated from the results of Fawcett et al (1970) for the transferred electron effect in pure GaAs at 300K. The ratio of the capture time in the (000) valley to that in the '100) valley is estimated to be about thirty from the measured extra-domain drift velocity, which was 4*105cm s-1 at temperatures around 150 K.