Study on high quality epitaxial growth of quantum well structures with II-VI diluted magnetic semiconductors

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The objective of the research is following:1.Fabrication of nanostructures of quantum wires, quantum dots and quantum wells, which are composed of II-VI compound diluted magnetic semiconductors.2.Study of exciton dynamics and optical spin injection in the nanostructures.For the above objective, we fabricated the quantum nanostructures with CdTe, CdSe, ZnTe, ZnSe and magnetic materials of Mn by using molecular expitaxy and hot wall epitaxy. Electron beam lithography method was also used for nanostructure fabrications. Fabricated quantum nanostructures were evaluated by x-ray diffraction and electron microscopy. Optical properties were studied by femtosecond laser spectroscopy in high magnetic fields. Ultrafast spin dynamics of excitons was investigated in these diluted magnetic nanostructures by transient pump-probe spectroscopy. The spin dynamics in the high density electron-hole plasma, excitons, and Mn ions were clarified in the femotsecond to nanosecond time region.Spin injection processes were investigated in CdTe-CdMnTe double quantum wells, where the transient photoluminescence of quantum-well excitons showed fast spin injection and spin relaxation processes.Magnet-optical properties and exciton dynamics were studied in the quantum wire structures of ZnMnSe. Marked confinement effect was observed in the narrow quantum wires. Spin switching processes were clarified in ZnTe-ZnMnTe spin superlattices, where the distribution of up- and down-spin states of excitons was spatially separated in ZnTe and ZnMnTe layers by the external magnetic fields. These phenomena have high possibilities for spin electronic applications.