EFFECT OF GROWTH-PHASE ON INTRINSIC STARK-EFFECT IN CDS-ZNSE SUPERLATTICES

The operation of the intrinsic Stark effect at visible wavelengths is reported, for both cubic and wurtzite type-II CdS-ZnSe strained layer superlattices grown on CdS buffer layers on (111)A GaAs. An observed i ncrease of the effective piezoelectric coefficient from the measured c ubic bulk value is attributed to a nonlinear effect, as previously rep orted for CdTe quantum wells [R. Andre, J. Cibert, Le Si Dang, J. Zema n, and M. Zigone, Phys. Rev. B 53, 6951 (1996)]. Exciton peak shifts o f 70 meV per decade change of excitation intensity are similar in magn itude to those found in CdS-CdSe superlattices of similar period. Thes e shifts are attributed to screening of the internal piezoelectric fie lds by photoexcited carriers. Exciton peak shifts that are smaller by an order of magnitude appear in CdS-ZnSe samples, grown on (100) ZnSe buffers and therefore predicted to exhibit no piezoelectric effects of any order. These small shifts, which we attribute to space charge bui ldup, are a characteristic feature of type-II superlattices. (C) 1997 American Institute of Physics.