HOLE DELOCALIZATION IN CDTE CD1-XZNXTE QUANTUM-WELLS

We report on femtosecond pump-probe absorption measurements in CdTe/Cd 1-xZnxTe quantum wells with an unusual distribution of band offset: al most all the band-gap difference between the two constituent materials is found as a conduction-band offset. We have observed a blueshift of the exciton energy due to hard-core repulsion between excitons and an intriguing redshift in the presence of free electron-hole pairs. We e valuate the redshift due to different mechanisms and conclude that the redshift observed is due to hole delocalization throughout the struct ure resulting from the very shallow valence-band potential wells.