ASYMMETRIC DOUBLE QUANTUM WELLS AS EXCITON SPIN SEPARATOR.

Exciton recombination in asymmetric CdMgTe/CdTe/CdMgTe/CdTe/CdMnTe double quantum wells (ADQW) with different barrier widths is studied in magnetic field up to 10 T. As grown structures were subjected to temperature annealing to introduce Mn and Mg atoms from the barriers into the CdTe quantum wells (QW). At low fields exciton transition in QW with magnetic impurity (Mn) is higher in energy than that in QW with nonmagnetic impurity (Mg), and interwell exciton relaxation is fast independently on the spin state. In contrast, at high fields, when the energy order reverses, an unexpectedly low relaxation rate of σ- polarized excitons from nonmagnetic QW to the ground σ+ polarized state in magnetic QW has been observed. Effect strongly correlates with hh–lh splitting value Δhh–lh and discussed in terms of valence band mixing. Such a slowing down of relaxation allows separation of oppositely polarized excitons in different QWs. [ABSTRACT FROM AUTHOR]