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 increase of the effective piezoelectric coefficient from the measured cubic bulk value is attributed to a nonlinear effect, as previously reported for CdTe quantum wells [R. Andre, J. Cibert, Le Si Dang, J. Zeman, and M. Zigone, Phys. Rev. B 53, 6951 (1996)]. Exciton peak shifts of 70 meV per decade change of excitation intensity are similar in magnitude to those found in CdS-CdSe superlattices of similar period. These shifts are attributed to screening of the internal piezoelectric fields 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 buildup, are a characteristic feature of type-II superlattices. (C) 1997 American Institute of Physics.