MAGNETOOPTICAL STUDIES OF THE TYPE-I TYPE-II CROSSOVER AND BAND-OFFSET IN ZNTE/ZN1-2MNXTE SUPERLATTICES IN MAGNETIC-FIELDS UP TO 45 T

We report measurements of magnetoreflectivity in ZnTe/Zn1-xMnxTe superlattices with varying well width in magnetic fields up to 45 T. From an analysis of the Zeeman splitting, we investigate the change of band alignment with field and the band offset ratio. A crossing of the is exciton transitions from the ZnTe buffer layer and the 1s heavy hole sigma(+) exciton of the superlattice is observed, providing unambiguous evidence of a band alignment change from type I to type II. The excitonic energy levels for both type-I and type-II band structure are calculated using a variational method. This model fits the experimental data very well at high fields for both sigma(+) and sigma(-) transitions and predicts that the type-I/type-II crossover occurs at 2-3 T. Also by fitting the sigma(+) transition energy as a function of held a conduction band offset ratio of Delta E(c)/Delta E(g)=0.72+/-0.04 is deduced.