Magneto-optical studies of the type I/type II crossover and band offset in ZnTe/Zn sub(1-x)Mn sub(x)Te superlattices in magnetic fields up to 45 T

We report measurements of magneto-reflectivity in ZnTe/Zn sub(1-x)Te superlattices in magnetic fields up to 45 Tesla. 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 1 s exciton transitions from the ZnTe buffer layer and the 1 s heavy hole sigma sub(+) 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 field for both sigma sub(+) and sigma sub(-) transitions. A conduction band offset ratio of Delta E sub(c)/ Delta E sub(g) identical with 0.72 plus or minus 0.04 is deduced.