TIME-RESOLVED OPTICAL STUDIES OF PIEZOELECTRIC EFFECTS IN WURTZITE STRAINED-LAYER SUPERLATTICES

CdS-CdSe multilayers form the only known example of a wurtzite, type II superlattice in which lattice strain generates giant piezoelectric fields which modify the band structure. The exciton luminescence band, ascribed to recombination of electrons in CdS layers with holes in CdSe layers, broadens and shifts to lower energy with increasing delay after excitation of the superlattice with a short pulse of light. These effects are interpreted in terms of dynamic band restructuring due to screening of the piezoelectric fields by photogenerated carriers.