Evidence for long-living charge carriers in electrically biased low-temperature-grown GaAs photoconductive switches

Low-temperature-grown GaAs continues to be one of the most important materials of ultrafast optoelectronics. Little is known, however, about the recombination dynamics of photogenerated charge carriers under the influence of an applied electric field, and it has remained unclear to what extent biased photoswitches exhibit field screening effects. Here, the authors investigate the screening in biased few-micrometer-sized photoconductive gaps quantitatively and find that it can amount to tens of percent of the applied field. They find that a subgroup of the photogenerated carriers recombines on an unexpectedly long excitation-density-dependent time scale of nanoseconds to tens of nanoseconds.