Ultrafast exciton dynamics in ternary II-VI semiconductor quantum wells

Ultrafast exciton dynamics is investigated in a high-quality ZnxCd1-xSe-ZnS e multiple quantum well at low photoexcited carrier density by means of a t wo-color femtosecond absorption saturation technique. Broadening of the exc iton Lines due to carrier photocreation is found to dominate the observed n onlinear response. Measurements performed as a function of the initial ener gy of the photoexcited carriers show that the dynamics of the induced broad ening strongly depends on the carrier distribution, suggesting that Pauli e xclusion principle effects significantly influence exciton broadening in te rnary quantum-well systems. Localized excitons are shown to modify the pico second nonlinear response, inducing a frequency shift of the absorption cha nge peak as the system approaches quasiequilibrium. [S0163-1829(99)00331-8] .