FORMATION OF TYPE-II EXCITONS IN CDTE CD1-XMNXTE SUPERLATTICES AT HIGH MAGNETIC-FIELDS/

We report measurements of magnetoreflectivity in CdTe/Cd1-xMnxTe super lattices with varying manganese concentration in magnetic fields up to 45 T. from an analysis of the 1s heavy-hole sigma(+) transition, we o bserve that the energy shift is directly equal to the shift in the val ence-band edge of the barrier layer. This provides a clear proof of ty pe-I-type-II crossover in this system. The critical magnetic field tha t leads to the formation of a type-II exciton is also estimated. We po int out that the criterion for the observation of a type-II exciton is that the type-II valence-band offset has to be larger than the bindin g energy of an exciton.