Biexciton formation induced by bright-dark exciton transitions in a diluted magnetic semiconductor asymmetric quantum well

We have investigated excitonic states in a (Cd,Mg)Te/CdTe/(Cd,Mn)Te asymmetric quantum well, during the photoluminescence decay processes. The intensity ratio of biexciton to exciton showed almost a linear dependence. The biexciton luminescence showed a longer decay time when compared with that of the exciton. The rate equations based on our model taking account of the dark exciton level (image) were used to analyze this anomalous exciton–biexciton system. Our analysis leads to a conclusion that the new channel from a dark exciton has an essential role when biexcitons are created in II–VI diluted magnetic semiconductor quantum wells.