ENHANCEMENT OF EXCHANGE INTERACTION IN ULTRATHIN CDS ZNS QUANTUM STRUCTURES/

In ultrathin, coherently strained CdS/ZnS single quantum wells the exc itonic exchange splitting is observed. An enhancement of more than one order of magnitude is found with respect to the bulk value. The excit onic states are identified by studying the photoluminescence polarizat ion and its dynamics. Spin flip times of about 100 ps are obtained. Ap plying 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.