Abstract

Low-temperature-grown GaAs (LT-GaAs) has long been known to have a (sub)picosecond photo-excited carrier response time. It has been suggested that the photo-excited carriers are trapped in such a short time due to EL2-like arsenic antisite defects or arsenic precipitates.¹ However, until now the electron and hole trapping times have not been separately determined. The ultrafast carrier recombination dynamics in the mid-gap states and the dynamic behavior of photoexcited holes are also not well understood. We report the first direct measurement of the hole trapping time from the valence band in LT-GaAs, and distinguish it from electron trapping time from the conduction band and recombination time. These results are compared with trapping and recombination times in conventional semi-insulating GaAs. We have also performed novel experiments at very high optical excitation densities (10^19-20 carriers/cm³) to time resolve the saturation dynamics of mid-gap states.

© 1996 Optical Society of America