Photoluminescence spectra of CdTe multi-quantum wells sandwiched by ultrathin MnTe layers and their temperature dependence

To study the energy transfer (ET) between the Mn2+ intra-center luminescence (IL) state and the band state in CdTe quantum wells (QWs), we studied the temperature dependences of the photoluminescence (PL) spectra of the CdTe multi-QWs sandwiched by ultrathin MnTe layers and found an anomalous thermal variation of their PL intensities. With elevating temperature, the PL intensities of the thinner QWs having 4 and 8 monolayers (MLs) remain at rather high temperatures than 100 K despite the PL of the thicker QWs disappears rapidly. In the thinner QWs, the PL bands appear in an overlap region with the Mn2+ IL-band and energy transfer is expected between the IL-state and the band states in the thinner QWs. The anomalous thermal variations of the PL intensities can be explained by considering the ET and the role of Mn2+ IL-state as reservoir states against the thermal quenching processes.