Enhancement of exchange interaction in ultrathin CdS/ZnS quantum structures

In ultrathin, coherently strained CdS/ZnS single quantum wells the excitonic exchange splitting is observed. An enhancement of more than one order of magnitude is found with respect to the bulk value. The excitonic states are identified by studying the photoluminescence polarization and its dynamics. Spin flip times of about 100 ps are obtained. Applying a quantum disc model, the observed exchange splitting energies correspond to lateral confinement geometries below the bulk excitonic Bohr radius a(B) thus revealing three-dimensional quantum confinement. (C) 1998 Published by Elsevier Science Ltd.