Type-II diluted magnetic semiconductor ZnMnTe quantum dots ͑QDs͒ in ZnSe matrix grown by molecular beam epitaxy were investigated by conventional and magnetophotoluminescence ͑PL͒ spectroscopy. The QD emission exhibits a type-II characteristic in excitation power dependence of PL peak energy. A nonzero circular polarization of PL at the absence of magnetic field was observed. This phenomenon is attributed to the accumulation of interface charges confined in adjacent layers. The magneto-optical measurement demonstrates a magnetic-induced degree of circular polarization in the PL spectra, indicating the Mn incorporation into the QD system.

Organic tris͑8-hydroxyquinoline͒aluminum ͑Alq3͒ amorphous layers are prepared by vacuum deposition at various substrate temperatures T sub from 30 to 180°C. The surface morphology and electrical characteristics of these as-deposited layers are studied by atomic force microscopy and current-density versus electric-field ͑J-E͒ curves. The temperature dependence of the dark electrical conductivity ͑T͒ determined from J-E curves is also examined. These experimental results reveal that the surface and electrical properties of Alq3 amorphous layers deposited at T sub between 90 and 120°C exhibit an anomalous T sub dependence. However, this anomalous T sub dependence is not observed from infrared absorption measurements, and therefore is not the result of chemical degradation. The observed behavior is explained in terms of the property that the vacuum deposition of Alq3 with T sub between 90 and 120°C involves a thermal interconversion between meridional and facial Alq3 isomers.

The morphology and the size-dependent photoluminescence (PL) spectra of the type-II ZnTe quantum dots (QDs) grown in a ZnSe matrix were obtained. The coverage of ZnTe varied from 2.5 to 3.5 monolayers (MLs). The PL peak energy decreased as the dot size increased. Excitation power and temperature-dependent PL spectra are used to characterize the optical properties of the ZnTe quantum dots. For 2.5-and 3.0-ML samples, the PL peak energy decreased monotonically as the temperature increased. However, for the 3.5-ML sample, the PL peak energy was initially blueshifted and then redshifted as the temperature increased above 40 K. Carrier thermalization and carrier transfer between QDs are used to explain the experimental data. A model of temperature-dependent linewidth broadening is employed to fit the high-temperature data. The activation energy, which was found by the simple PL intensity quenching model, of the 2.5, 3.0, and 3.5 MLs were determined to be 6.35, 9.40, and 18.87 meV, respectively.

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In this study, various Alq 3 amorphous layers are prepared by vacuum deposition at different substrate temperatures T sub . The surface morphology, structural information, and electrical and optical properties of these as-deposited layers are studied by atomic force microscopy, X-ray diffraction, J-E curves, and photoluminescence studies, respectively. The optimum deposition conditions for Alq 3 amorphous layers with respect to T sub are also discussed.