Ultrafast carrier trapping in Er-doped and Er,O-codoped GaAs revealed by pump and probe technique

Dynamics of photoexcited carriers in Er-doped GaAs (GaAs:Er) and Er,O-codoped GaAs (GaAs:Er,O) have been systematically investigated by means of a pump and probe technique. A characteristic ps-scale relaxation was clearly observed in transient reflectance (dR/R) and transmission (dT/T) curves. The relaxation was due to the trapping of photoexcited carriers by an Er-related trap, which was closely related to efficiency of Er3+ luminescence.