Dynamical spin separation in a double quantum well of diluted magnetic semiconductor due to spin-dependent type-II band alignment

Dynamical spin separation is studied in a double quantum well composed of diluted magnetic semiconductor (DMS) of Zn0.71Cd0.26Mn0.03Se and non-magnetic Zn0.73Cd0.27Se, by means of time-resolved circularly polarized photoluminescence (PL). The giant Zeeman shift of excitonic PL with σ+-circular polarization increases with increasing magnetic field, indicating the type-II transition between an electron in the Zn0.73Cd0.27Se and a heavy hole (hh) in the DMS with down-spin states. Excitonic PL due to the type-I transition inside the Zn0.73Cd0.27Se well is simultaneously observed with σ− polarization. The lifetime of the type-II transition increases from 70 to 140 ps with increasing field up to 3.5 T and then saturates. These results show spatial separation of the hh-spins, which is sustained by a relatively slow injection time of 300 ps of the hh-spin from the Zn0.73Cd0.27Se to the DMS wells.