Dynamics of Trapping, Trap-Emptying, and Breakdown in LT GaAs

Photoconductors fabricated from annealed low-temperature-grown GaAs (LT GaAs) represent the state-of-the-art in ultrafast photodetectors due to sub-ps carrier trapping, high responsivity and high breakdown voltage.1 Much attention has been paid to measurement of the trapping time. However, the properties of the trapped charges and their influence on carrier transport has not been studied. In this paper, we investigate the dynamics of trapping, trap-emptying and breakdown in LT GaAs interdigitated photoconductors, and obtain clear evidence for field screening by trapped carriers and for avalanche breakdown. The effect of the trap-emptying time on the transport is revealed by comparison of the dynamical results with the temperature dependence of the dark current.