Epitaxial II-VI semiconductor quantum structures involving dilute magnetic semiconductors

Magneto-optical properties were studied on ultrathin MBE-grown ZnTe and ZnSe epilayers by observing hydrogenic exciton series up to 2s states in the absence of the magnetic field and by observing Landau level transitions in the magnetic field. The band structure of ZnSeTe superlattice with sinusoidal energy profiles was investigated by using nearly-free-electron (NFE) approximation. The analysis revealed that the minigap is determined only by the value of the band offset of the sinusoidal superlattice. The quantum effect arising from such band structures of sinusoidal superlattice was observed in photoluminescence spectrum, which shifted to lower energy relative to the corresponding alloy system. The quantum effect was further investigated in the zero-dimensional geometries -- the so called “quantum dots” (QDs) -- in which the motion of carriers and/or excitons are confined in all three directions. The characteristics of QD system was observed via thermal stability and narrow linewidth of optical transition. The degree of wavefunction localization in the QDs was mapped by involving diluted magnetic semiconductor, which showed extremely large Zeeman splitting of electronic levels, in the QD system. The spin-spin interaction in coupled QD system was further investigated by using double layer QD (DLQD) structure consists of DMS (ZnCdMnSe) and non-DMS (CdZnSe) QDs with non-DMS (ZnSe) barriers. The twice larger spin polarization of carriers in non-DMS CdZnSe QDs was observed in DLQD system compared to that of single layer CdZnSe DQs, indicating significant enhancement of spin polarization due to the presence of highly spin-polarized carriers in DMS QDs.