HOT EXCITON RELAXATION IN CDZNSE ZNSE QUANTUM-WELLS AND QUANTUM DOTS/

The dimensionality dependence of hot exciton relaxation has been studi ed by means of time-resolved photoluminescence and photoluminescence e xcitation spectroscopy comparing CdZnSe/ZnSe quantum wells and quantum dots. An energetically narrow exciton distribution within the inhomog eneously broadened luminescence band is prepared by low density laser excitation with an excess energy corresponding to an integer number of LO phonons. In quantum wells, lateral migration of excitons within th e layer causes a transient redistribution of excitons in energy contro lled by acoustic phonon interaction. This is indicated by a spectral b roadening and a rid shift of the PL signal with time. In contrast, thi s process is found to be substantially suppressed in quantum dots due to the three-dimensional exciton confinement. (C) 1998 Elsevier Scienc e B.V. All rights reserved.