Power and temperature dependent magneto-photoluminescence of the asymmetric double layers of quantumdots

Excitation power and temperature dependent magneto-photoluminescence experiments have been performed on a double-layer quantum dot (QD) system, in which two QD layers are composed of CdSe and CdZnSe layers. The photoluminescence (PL) peaks from two QD layers are well resolved in the spectra. The relative PL intensity of the two QD layers depends strongly on excitation power, indicating carrier transfer between the two QD layers. The intensity of the PL peak undergoes a significant change when one circular polarization is selected under a magnetic field. Specifically, the PL from both QD layers shows a stronger intensity for the σ^- than for the σ circular polarizations due to the spin polarization of the carriers in the presence of a magnetic field. The difference of PL intensity between the two polarizations showed a significant dependence both on excitation power and temperature. Furthermore, the degree of polarization from the CdSe QDs was much larger than that from the CdZnSe QDs. Such polarization phenomena in PL effects are discussed in terms of thermal effects and spin interactions between the carriers in the pairs ofQDs.