Picosecond dynamics of low density excitons in GaAs quantum wells

Time-resolved photoluminescence (PL) measurements were performed on a multiple GaAs/AlGaAs quantum well structure. The rise and decay profiles of PL centered at the free exciton line and the impurity related excitonic-complex line were investigated as a function of temperature at a low excitation density (10(9) cm(-2)). This study provides new information on how excitons are captured by impurities and on the kinetics of excitonic-complex formation and annihilation. The exciton capture time by impurities is about 250 ps and independent of temperature (< 80 K) when the exciton density is comparable to the residual impurity density.