Non-equilibrium dynamical behavior of exciton/biexciton in a diluted magnetic semiconductor asymmetric quantum well

Optical properties of a (Cd,Mg)Te/CdTe/(Cd,Mn)Te quantum well is investigated systematically using photoluminescence (PL) and time-resolved photoluminescence (TRPL). The PL intensity ratio of biexciton to exciton showed a linear dependence. The biexciton TRPL showed a longer lifetime as compared with that of the exciton. These results suggested an important role of dark excitons and their spin scattering by Mn localized spins in this system. The rate equations based on our model taking account of the dark exciton level (J=±2) were used to analyze the time decay of the exciton and biexciton TRPL in various temperatures and excitation densities. Our analysis leads to a conclusion that the new channel from a dark exciton has an essential role when biexcitons are created in dilute magnetic semiconductor quantum wells containing Mn in the barrier.