MAGNETIC-FIELD DEPENDENCE OF THE EXCITON TRANSFER IN SEMIMAGNETIC DOUBLE-QUANTUM-WELL STRUCTURES

The energy transfer between the wells of asymmetric CdTe/Cd1-xMnxTe do uble quantum well structures was investigated by both CW and time-reso lved optical measurements. The barrier heights were tuned by an extern al magnetic field. Furthermore, in samples with a wide semimagnetic we ll magnetic fields caused resonances and level crossings of the electr on and hole energies. This was observed in the magnetic field dependen ce of the CW luminescence and luminescence excitation intensities of t he respective transitions. The luminescence decay was measured using s elective ps excitation. In the case of a field induced resonance we go t a strong decrease of the decay time constant as a function of the ma gnetic field. A kinetic model for the exciton transfer is given taking into account the independent tunnelling of electrons and holes and th e exciton lifetimes in both wells. A set of rate equations describe th e time dependent carrier densities in the quantum wells. The solutions are given for CW and ps excitation.