Femtosecond Dynamics of Resonantly Excited Room Temperature Excitons in II-VI CdZnTe/ZnTe Quantum Wells

We report the first direct measurement of the relative bleaching strength of excitonic absorption by "cool" free e-h pairs and cold excitons. For this study, wide-gap II-VI CdZnTe/ZnTe quantum wells are uniquely qualified since, in addition to the presence of well-defined room temperature excitonic absorption peaks, the exciton binding energy, the longitudinal-optic phonon energy and the thermal energy at room temperature are all comparable and thus the ionized electron-hole pairs are "cool" in this system, in contrast to the "hot" ionized electron-hole pairs generated in III-V quantum wells.