ELECTRIC-FIELD-INDUCED ABSORPTION MODULATION OF CDS QUANTUM DOTS IN AN ORGANIC MATRIX

CdS quantum dots under weak confinement conditions embedded in a polyv inyl alcohol (PVA) polymer film have been studied in the presence of a n external electrical field at different densities of photoexcited car riers. Applying an external electric field strength of 5 X 10(4) V/cm, the observed absorption change DELTAalpha/alpha in this material is a pproximately 7%. At high laser excitation the electric field separates the laser excited carriers and the change in absorption is attributed to a compensation of the many-particle interaction by the external el ectrical field. A restoring of the oscillator strength is observed and explained by screening effects of the polarization fields in the inte rface region due to the photogenerated electron-hole pairs.