Magnetic polarons in type-II (Zn,Mn)Se/ZnTe quantum dots*

We have studied magnetic polaron formation dynamics in (Zn,Mn)Se/ZnTe quantum dots$^{\mathrm{2}}$ (QDs) using time-resolved photoluminescence (TRPL) spectroscopy. The emitted light was spectrally and temporally analyzed; the emission spectra were recorded as function of time delay ($\Delta t)$ from the exciting laser pulse. The recombination time at $T=$10 K in our samples is 2.3 ns. The peak energy of the emission red shifts with increasing $\Delta t $due to the lowering of the hole-Mn spin complex (magnetic polaron) energy. From this shift we determined the magnetic polaron formation energy ($E_{MP})$ at $T=$10 K to be 20 meV, which is half the value observed in the ZnSe/(Zn,Mn)Te system studied previously.$^{\mathrm{3}} \quad E_{MP\thinspace }$decreases with increasing temperature, in contrast to the behavior of the ZnSe/(Zn,Mn)Te system$^{\mathrm{3}}$ in which $E_{MP}$ is temperature independent. These results are discussed in terms of a theoretical model. [2] L. Lee, et al., J. Cryst. Growth \textbf{378}, 222 (2013). [3] I. R. Sellers, et al., Phys. Rev. B \textbf{82}, 195320 (2010).