Femtosecond dynamics of resonantly excited room-temperature excitons in II-VI CdZnTe/ZnTe quantum wells

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Abstract
The femtosecond pump-and-probe technique, with 14-fs probe pulses, was used to measure exciton dynamics utilizing the unique characteristics of II-VI CdZnTe/ZnTe quantum wells, at room temperature. We have found that the bleaching effect of ‘‘cold’’ neutral excitons on excitons is stronger than that of the same density of ‘‘cool’’ uncorrelated charged electron-hole pairs, in disagreement with predictions. We find strong evidence, however, that long-range Coulomb screening is negligible in quasi-2D quantum wells. Additionally, we have measured a very fast exciton ionization time of 110 fs.