Observation of long-lived exciton magnetic polarons in ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Se/ZnSe multiple quantum wells

Using time-resolved photoluminescence to study ${\mathrm{Zn}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Se/ZnSe multiple quantum wells, we show that the formation and decay kinetics of exciton magnetic polarons (EMP’s) depend strongly upon the Mn concentration. We suggest that as the Mn ion concentration in the barrier is increased, three different types of EMP may form: (i) both the electron and hole are confined to the magnetic material (type-I EMP), (ii) the electron and hole are spatially separated (type-II EMP), or (iii) confined at the interface. In agreement with previous results in thick epilayers, we find that both the formation time and recombination lifetime of the type-I EMP are approximately 400 ps, so that the majority of the EMP’s never fully achieve their equilibrium configuration. In contrast, the recombination lifetime of the spatially indirect type-II EMP observed here is greater than 20 ns (nearly forty times the formation time), so that the EMP’s in quantun wells may be studied in thermal equilibrium.