CDS-ZNSE INTRINSIC STARK SUPERLATTICES

Type-II CdS-ZnSe strained layer superlattice (SLS) grown on a CdS buff er on (1 1 1)A GaAs provide evidence for the intrinsic Stark effect at visible wavelengths. Shifts in photoluminescence (PL) peak energies a re expected when photoexcited carriers screen the internally generated piezoelectric fields. Characteristic PL blue shifts under increasing excitation for CdS-ZnSe samples are observed. Transmission electron mi crographs show that a superlattice, grown at 400 degrees C, is mostly hexagonal in structure but a similar sample, grown at 300 degrees C, a dopts a cubic habit. However, both samples show similar shift factors, 70 meV per decade of excitation intensity, in the range of power dens ities from 50 mW cm(-2) to 20 kW cm(-2). These shift factors are only slightly smaller than that found in CdS-CdSe hexagonal superlattices o f similar period. This result is not expected since the bulk piezoelec tric coefficients of cubic ZnSe are thought to be much smaller than th ose for wurtzite phase II-VI semiconductors. A resolution of these app arent contradictions may be found by involving the recently reported n onlinearity of cubic piezoelectric coefficients as a function of strai n by Andre et al. (C) 1998 Published by Elsevier Science B.V. All righ ts reserved.