The photoluminescence properties of antiferromagnetic EuTe layers grown by molecular-beam epitaxy are reported. At low temperatures, two excitonic photoluminescence peaks are observed at 1.92 and 1.88 eV with a full width at half maximum of about 10 meV. With applied magnetic field, these excitonic transitions shift linearly by Ϫ34 meV/T to smaller transition energies with a total shift of more than 240 meV at 7.2 T. This is the largest tuning range observed in any semiconductor. The observed magnetic field and temperature dependence of the luminescence lines is explained by the formation of large magnetic polarons due to exchange interactions between the d-like electrons in the conduction band and localized 4 f spins.

The properties of superlattices consisting of 2 monolayer wide CdTe insertions into ZnTe spacer barriers with thickness ranging from 3 to 75 monolayers are investigated by means of transmission electron microscopy and photoluminescence spectroscopy. We show that quasi zero-dimensional CdTe islands form in this highly lattice-mismatched system. For spacer thickness smaller than 25 monolayers, the islands are vertically correlated along the axis tilted by 40° with respect to the growth direction, while for thicker ZnTe spacers no correlation is observed. The electronic coupling between the correlated islands manifests itself by the appearing of an additional emission band at energies lower to those corresponding to uncorrelated dots. The optical spectroscopy data reveal zero-dimensional localization of excitons by the electronically coupled islands. The decay time of the excitonic recombination is found to be over an order of magnitude longer in the case of the coupled islands than in the case of isolated ones.

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Magnetic-ion-containing self-assembled quantum dots based on II-VI semiconductors are investigated by time-resolved optical spectroscopy. It is found that the dynamical properties of excitons confined in quantum dots depend on the relative position of intra-Mn transition with respect to the quantum-dot-related emission. When the intra-Mn transition energy is smaller than the dot emission energy, then the decay time of excitons in quantum dots increases with increasing magnetic field. When the intra-Mn transition energy is larger, no influence of the magnetic field on the recombination dynamics of excitons is found. The first case corresponds to CdMnSe/ZnSe structures, while the second one is observed in CdMnTe/ZnTe magnetic quantum dots.Introduction Incorporation of magnetic ions in semiconductor self-assembled quantum dots (QDs) opens a new and interesting field in QD physics. Such structures could, for example, permit one to investigate the interaction of strongly localized carriers with their magnetic environment [1]. The presence of magnetic ions also changes the dynamical properties of the QD system [2]. In recent years several methods have been developed to obtain semimagnetic quantum dots. They were produced either by wet chemical etching of lithographically patterned structures [3], or by selective annealing of single quantum wells (QWs) [4,5]. Yet another possibility is to take advantage of the presence of quantum well thickness fluctuations, i.e., to use so-called naturally formed quantum dots [1].In this report we present continuous-wave as well as time-resolved photoluminescence (PL) results obtained for self-assembled CdMnSe and CdMnTe QDs grown by molecular beam epitaxy (MBE). It is found, in particular, that the excitons in QDs exhibit different dynamical properties, depending on the energy of the QD-related PL with respect to the intra-Mn transition.