Ultrafast photoexcited carrier dynamics in GaAs:Er,O by pump and probe transmission spectroscopy

Abstract

AbstractUltrafast dynamics of photoexcited carriers in Er,O‐codoped GaAs (GaAs:Er,O) and Er‐doped GaAs (GaAs:Er) have been investigated by means of pump and probe transmission spectroscopy, and discussed in relation to Er‐related photoluminescence (PL) intensity. Time‐resolved transmission signal in undoped GaAs showed a temporal increase due to saturation of optical absorption, and then decreased reflecting the recovery of the absorption. The decrease consisted of two components corresponding to intra‐band relaxation (< 1 ps) and inter‐band relaxation (> 50 ps). In GaAs:Er,O and GaAs:Er, on the other hand, an additional component was observed. The relaxation time was 4 ∼ 11 ps. This relaxation time, assigned to carrier trapping time by an Er‐related trapping, became short with increasing Er‐related PL intensity. These results suggest the fast carrier capturing plays an important role for the enhancement of the Er‐related luminescence. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)