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  • 1
    Electronic Resource
    Electronic Resource
    Interface properties and in-plane linear photoluminescence polarization in highly excited type-II ZnSe/BeTe heterostructures with equivalent and nonequivalent interfaces (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 652-657 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Properties of interfaces with no-common atom in type-II ZnSe/BeTe heterostructures are studied with polarization spectroscopy. Structures with four possible configurations of normal and inverted interfaces have been investigated. Radiative recombination and its polarization anisotropy have been found to depend crucially on the interface configuration and excitation power. The comparison of interfaces formed by the growth on anion (Se, Te) and cation (Zn, Be) terminated layers has shown that the latter demonstrate a significantly higher nonradiative recombination rate. In agreement with the quantum well (QW) symmetry, the photoluminescence (PL) of the structures with nonequivalent normal and inverted interfaces is highly linearly polarized both at low and high excitation densities. Unexpectedly, a similarly strong PL polarization has been found for structures with equivalent interfaces up to carrier densities of 1012 cm−2 per QW. The polarization is explained by a built-in electric field, it decreases with increasing carrier concentration due to screening of the electric field. Finally, we have found that the PL polarization degree at interfaces with Be–Se and Zn–Te bonds amounts to about 50% and (approximate)70%, respectively.© 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1421039
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetics of radiative recombination in strongly excited ZnSe/BeTe superlattices with a type-II band alignment (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 1231-1233 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report results of a detailed investigation of type-II superlattices under high density photoexcitation. A strong spectral shift ((approximate)0.5 eV) of the recombination band corresponding to the indirect transition from the ZnSe conduction band to the BeTe valence band in ZnSe/BeTe superlattices with increasing carrier density has been found at T=300 K. The dynamical characteristics of this transition are studied by time-resolved spectroscopy. A model which accounts for the dependence of band bending and lifetimes of spatially separated electrons and holes on the concentration of the photoexcited carriers is developed. Numerical simulations of the photoluminescence kinetics are in very good agreement with experimental results. It turns out that despite the huge band offsets involved, the radiative recombination under high excitation conditions can be nearly as fast as in spatially direct quantum wells. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.124651
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  • 3
    Electronic Resource
    Electronic Resource
    Optical spectroscopy on individual CdSe/ZnMnSe quantum dots (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 524-526 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optical single dot studies in wide-band gap diluted magnetic CdSe/ZnMnSe quantum dots have been performed. Due to the sample design, the photoluminescence energy of the quantum dot signal is energetically below the internal Mn2+ transition, resulting in high quantum efficiencies comparable to nonmagnetic CdSe/ZnSe quantum dots. Magnetic-field- and temperature-dependent measurements on individual dots clearly demonstrate the exchange interaction between single excitons and individual Mn2+ ions, resulting in a giant Zeeman effect and a formation of quasi-zero-dimensional magnetic polarons. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1387256
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  • 4
    Electronic Resource
    Electronic Resource
    Strong coupling in a single quantum dot–semiconductor microcavity system (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 432 (2004), S. 197-200 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Cavity quantum electrodynamics, a central research field in optics and solid-state physics, addresses properties of atom-like emitters in cavities and can be divided into a weak and a strong coupling regime. For weak coupling, the spontaneous emission can be enhanced or reduced compared with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02969
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  • 5
    Electronic Resource
    Electronic Resource
    Interparticle interaction in spin-aligned and spin-degenerate exciton systems in II–VI quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1543-1547 
    Details
    ISSN: 0392-6737
    Keywords: Studies of specific magnetic materials ; Optical properties of thin films surfaces and layer structures (superlattices, heterojunctions and multilayers) ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Two qualitatively different e-h systems have been investigated in undoped CdTe/Cd0.88Mn0.12Te and Cd0.97Mn0.03 Te/Cd0.75Mn0.25 Te QWs at 2 K and magnetic fields up to 14 T, namely a strongly spin-depolarized system in the CdTe QW and a highly spin-polarized one in the Cd0.97Mn0.03 Te QW. The interaction of the spin-aligned excitons is repulsive. In contrast, in the spectra of a dense spin-depolarized excitonic system an additional well pronounced emission lineM was observed at approximately 5 meV below the excitonic line. This line is assigned to the emission of molecules consisting of excitons with opposite spins of both electrons and holes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457241
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic-field-induced dissociation of bound excitons in semi-magnetic semiconductor quantum wells (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1549-1553 
    Details
    ISSN: 0392-6737
    Keywords: Studies of specific magnetic materials ; Excitons and related phenomena (including electron-hole drops) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The influence of the electron spin splitting on the stability of quasi-two-dimensional donor bound excitons (D 0 X) has been investigated in the Cd0.97Mn0.03Te/Cd0.7Mg0.3Te semi-magnetic semiconductor quantum well (QW) structure. TheD 0 X binding energy has been measured directly from emission spectra recorded at magnetic field parallel to the QW plane. Complexes have been shown to dissociate into a neutral donor and a free exciton with a spin flip of the electron at high magnetic fields when the electron spin splitting exceeds the binding energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02457242
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  • 7
    Electronic Resource
    Electronic Resource
    Magnetic excitons in near-surface quantum wells: Experiment and theory (1998)
    Springer
    Physics of the solid state 40 (1998), S. 740-742 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured the photoluminescence spectra and photoluminescence excitation spectra of magnetic excitons in InGaAs/GaAs near-surface quantum wells in a magnetic field. We have quantitatively investigated the effect of dielectric enhancement of excitons in quantum wells brought about by decreasing the thickness of the barrier layer, both in a magnetic field and without.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130436
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  • 8
    Electronic Resource
    Electronic Resource
    Exciton-photon interaction in low-dimensional semiconductor microcavities (1998)
    Springer
    Journal of experimental and theoretical physics 87 (1998), S. 723-730 
    Details
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The structure of the photon states and dispersion of cavity polaritons in semiconductor microcavities with two-dimensional optical confinement (photon wires), fabricated from planar Bragg structures with a quantum well in the active layer, are investigated by measuring the angular dependence of the photoluminescence spectra. The size quantization of light due to the wavelength-commensurate lateral dimension of the cavity causes additional photon modes to appear. The dispersion of polaritons in photon wires is found to agree qualitatively with the prediction for wires having an ideal quantum well, for which the spectrum is formed by pairwise interaction between exciton and photon modes of like spatial symmetry. The weak influence of the exciton symmetry-breaking random potential in the quantum well indicates a mechanism of polariton production through light-induced collective exciton states. This phenomenon is possible because the light wavelength is large in comparison with the exciton radius and the dephasing time of the collective exciton state is long.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.558714
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  • 9
    Electronic Resource
    Electronic Resource
    Quantum dot multiexcitons in a magnetic field (1997)
    Springer
    JETP letters 66 (1997), S. 285-290 
    Details
    ISSN: 1090-6487
    Keywords: 73.61.Ey ; 71.35.Ji
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Multiexcitons confined in InGaAs/GaAs quantum dots (QDs) with a lateral size slightly exceeding the exciton Bohr radius are investigated by magnetophotoluminescence spectroscopy at 2 K. The Coulomb correlations in the two-exciton complex result in an additional confinement, which increases with decreasing dot size, while a magnetic field reduces this effect. A three-exciton complex is confined only by the geometric confinement potential of the QD. The exciton-exciton repulsion increases with decreasing dot size, while a magnetic field decreases the repulsion strongly when the magnetic length becomes smaller than the lateral size of the QD. A shell model for the QD multiexciton states is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567469
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  • 10
    Electronic Resource
    Electronic Resource
    Spin relaxation of Mn ions in (CdMn)Te/(CdMg)Te quantum wells under picosecond optical pumping (1997)
    Springer
    Journal of experimental and theoretical physics 85 (1997), S. 784-796 
    Details
    ISSN: 1090-6509
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spin relaxation of Mn ions in a Cd0.97Mn0.03Te/Cd0.75Mg0.25Te quantum well with photogenerated quasi-two-dimensional electron-hole plasma at liquid helium temperatures in an external magnetic field has been investigated. Heating of Mn ions by photogenerated carriers due to spin and energy exchange between the hot electron-hole plasma and Mn ions through direct sd-interaction between electron and Mn spins has been detected. This process has a short characteristic time of about 4 ns, which leads to appreciable heating of the Mn spin subsystem in about 0.5 ns. Even under uniform excitation of a dense electron-hole plasma, the Mn heating is spatially nonuniform, and leads to formation of spin domains in the quantum well magnetic subsystem. The relaxation time of spin domains after pulsed excitation is measured to be about 70 ns. Energy relaxation of excitons in the random exchange potential due to spin domains results from exciton diffusion in magnetic field B=14 T with a characteristic time of 1 to 4 ns. The relaxation time decreases with decreasing optical pump power, which indicates smaller dimensions of spin domains. In weak magnetic fields (B=2 T) a slow down in the exciton diffusion to 15 ns has been detected. This slow down is due to exciton binding to neutral donors (formation of bound excitons) and smaller spin domain amplitudes in low magnetic fields. The optically determined spin-lattice relaxation time of Mn ions in a magnetic field of 14 T is 270±10 and 16±7 ns for Mn concentrations of 3% and 12%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.558366
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