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Single Quantum (single + quantum)

Distribution by Scientific Domains
Physics and Astronomy100%

Terms modified by Single Quantum

  • single quantum coherence
    		•
  • single quantum dot
    		•
  • single quantum well
    		•

    Selected Abstracts

    The growth of In-rich InGaN/GaN single quantum wells by metalorganic chemical vapor deposition

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003
    Hyun Jin Kim
    Abstract In-rich InGaN/GaN single quantum wells were grown by metalorganic chemical vapor deposition for the first time to the best of our knowledge. The structures consist of a 2-,m thick GaN buffer layer, a 2-nm thick In-rich InGaN single quantum well, and a 20 nm thick GaN capping layer. Single quantum well structures were examined by transmission electron microscopy. Photoluminescence emissions from the single quantum well samples were observed at wavelengths ranged from 400 nm to 500 nm depending upon the growth conditions of the InN layer. From a simple energy level calculation, we found the possibility of extremely large emission peak shift with well thickness. [source]

    Confinement of magnetoexcitons in GaAs quantum well with a superconducting disk on top of the well

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 15 2006
    Z. G. Koinov
    Abstract We study the confinement of magnetoexcitons in quantum wells in the presence of a strong external homogeneous magnetic field and a cylindrical symmetric inhomogeneous magnetic field created by a superconducting disk, placed on the top of the well. We calculate numerically the trapping energy and the corresponding center-of-mass wave function of magnetoexcitons in a GaAs single quantum well. The calculations clearly indicate the formation of bound exciton states with nonzero values for the center-of-mass exciton wave function only in a sufficiently small area. This effect of exciton trapping can be used to design new functional nanoelectronic devices. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Contactless electroreflectance studies of II,VI nanostructures grown by molecular beam epitaxy

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004
    Martín Muñoz
    Abstract The interband transitions of a single quantum well structure of Zn0.53Cd0.47Se/Zn0.27Cd0.23Mg0.50Se, lattice matched to InP, and of a capped CdSe quantum dot structure have been investigated using contactless electroreflectance. From a comparison of the quantum well optical transitions with those calculated using the envelope function approximation we determined the band offsets for this system. The electroreflectance spectrum of the quantum dot structure shows transitions originating from all the portions of the sample including the quantum dots and the wetting layer. Assuming a lens shape geometry and that the effective height-to-radius ratio observed in uncapped quantum dots is preserved, the size of the capped quantum dots was determined using the observed electroreflectance transitions, and the effective mass approximation. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Transport mechanism in the quantum well embedded with quantum dots

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009
    E. S. Kannan
    Abstract Electron transport in single and double quantum well system embedded with InAs quantum dots is investigated by carrying out magnetoresistance measurements at 1.2 K. At low carrier densities, the electrons are strongly localized due to disorder and undergo magnetic field induced insulator to quantum Hall liquid transitions characterized by temperature independent crossing points. At higher carrier densities no such magnetic field induced transition are observed. The potential induced by the electrons in the quantum dots were found to enhance the scattering between the edge states resulting in the substantial reduction of the width of the Hall plateau in the single quantum well system. In the double quantum well system, instead of plateaus abrupt increase in the Hall resistance is observed at integer filling factors. On sweeping the gate bias at fixed magnetic field, hysteresis effect was observed in the double quantum well system due to the charge trapping in the defect levels. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Time-resolved photoinduced Kerr rotation in semiconductor microcavity

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2009
    Y. Mitsumori
    Abstract We studied photoinduced Kerr effect in cavity polaritons in a semiconductor microcavity by carefully measuring the time-resolved Kerr rotation and ellipticity spectra. The Kerr rotation angle of the microcavity polaritons is a hundred times larger than a conventional single quantum well. A spectral shape analysis of the observed spectra suggests that the photoindeced Kerr effect mainly results from a line broadening of the polarions due to spin-polarized polariton-polariton scattering. Enhancement in oscillator strength also contributes to the large rotation angle. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Nuclear field effect on the spin dynamics of electron localized on a donor in a single quantum well

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2008
    C. Testelin
    Abstract We use photoinduced Faraday rotation (PFR) in presence of an applied magnetic field to study the spin dynamics of localized electrons. The sample is a CdTe/CdMgTe quantum well (QW) of width 80 Å containing a layer of iodine donors at its center, with concentration 1011 cm,2. The spin polarization of donor-bound electrons is built via the optical polarization of donor-bound excitons, their hole spin relaxation, and their recombination. In a transverse (in-plane) magnetic field, PFR shows damped Larmor oscillations from which we deduce a 18 ns electron-spin decoherence time, and a transverse Landé factor of 1.29. In addition, for oblique optical incidence the electron-nuclei hyperfine interaction builds a nuclear spin polarization in presence of polarized electrons. This leads to the construction of an effective magnetic field, the Overhauser field, acting on the electronic spins. The Larmor frequency is then different for ,+ or ,, polarizations of the exciting light. The dependence of the phenomenon on the optical incidence allows the determination of the maximal Overhauser field, which is about 10 mT, at least two orders of magnitude weaker than for III-V semiconductors. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Time-resolved photoluminescence and steady-state optical studies of GaInNAs and GaInAs single quantum wells

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2007
    Y. Sun
    Abstract Time-resolved photoluminescence spectroscopy is used to investigate carrier dynamics of Ga1,xInxNyAs1,y (x , 0.33, y , 0.01) single quantum well (QW) structures. PL spectra measured as a function of temperature together with the PL decay times at wavelengths around and below the PL peak energy are used to determine de-trapping activation energies and time constants. The results are interpreted in terms of simultaneous thermal excitation of deep localized excitons to shallow localized states. According to the model, with increasing temperatures, localized excitons gain enough thermal energy to populate the free exciton states in quantum well with shorter lifetimes due to coherent nature of free excitons. In addition, at temperatures around and above 80 K, more non-radiative channels become available to compete with the radiative processes leading to shorter time constants. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Optimizing the internal quantum efficiency of GaInN SQW structures for green light emitters

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006
    D. Fuhrmann
    Abstract GaxIn1,xN/GaN single quantum well (QW) structures emitting in the range of 450 nm to 620 nm have been grown by MOVPE. Temperature and excitation power dependent photoluminescence (PL) was used to determine the internal quantum efficiency (IQE) for these structures. For the blue emitting QWs high IQE values on the order of 60% were achieved. Due to a reduced growth temperature, reduced growth rate and increased V/III ratio we obtained QWs with good morphology and high In content above 25%. Thinner QWs with high In content showed a clear improvement of IQE compared to QW-structures with larger thickness but smaller In-content emitting at the same wavelength. Between ,peak = 460 nm and 530 nm we observed a slight reduction in IQE with values of 58% at 490 nm and 40% at 525 nm. But towards ,peak = 620 nm IQE decreased due to the electric field induced separation of the electron and hole wavefunction down to 1%. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Stimulated emission and leakage current in InxGa1,xN lasers

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2005
    Elis Mon
    Abstract In this paper we calculate the temperature dependence of the transparency concentration n0 for InxGa1,xN/GaN single quantum well laser diodes. To establish the lasing mechanism existing in these lasers, this concentration is compared with that given by the Mott criterion limiting the existence of an excitonic gas or electron-hole plasma. For a typical structure with an In0.13Ga0.87N active layer n0 results higher than the critical excitonic concentration. This result indicates that the conventional electron-hole plasma instead of excitonic recombination is the dominant mechanism responsible for lasing in nitride lasers. The contribution of the diffusion leakage current density to the total threshold current density was also calculated, considering both electron and hole components. We obtain that the electron leakage current density is more than a half of the total threshold current density, confirming it is the main loss mechanism present in these lasers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Analysis of self-pulsation characteristics of InGaN laser diode

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003
    V. Z. Tronciu
    Abstract Self-pulsation characteristics of InGaN laser diode emitting at 395 nm wavelength are investigated theoretically and experimentally. The laser structure consists of a multi-quantum well InGaN active layer and an InGaN single quantum well saturable absorber. Self-pulsations with the frequency range from 1.6 to 2.9 GHz have been obtained. The results show a good agreement between measured and calculated characteristics of self-pulsation. We also discuss the impact of the saturable absorber on the laser dynamics. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Effect of growth interruption on In-rich InGaN/GaN single quantum well structures

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003
    Soon-Yong Kwon
    Abstract We successfully grew In-rich InGaN/GaN single quantum well structures by metal-organic chemical vapor deposition and confirmed their formation by optical and structural measurements. Relatively high growth temperature (730 °C) for InGaN layer facilitated the formation of 2-dimensional quantum well structures, presumably due to high adatom mobility. As the growth interruption time increased, the PL emission efficiency from InGaN layer improved with peak position blue-shifted and the dislocation density decreased by one order of magnitude. The high resolution cross-sectional TEM images clearly showed that the In-rich InGaN layer thickness reduced from 2.5 nm (without GI) to about 1 nm (with 10 s GI) and the InGaN/GaN interface became very flat with 10 s GI. We suggest that decomposition and mass transport processes on InGaN during GI is responsible for these phenomena. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    The growth of In-rich InGaN/GaN single quantum wells by metalorganic chemical vapor deposition

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003
    Hyun Jin Kim
    Abstract In-rich InGaN/GaN single quantum wells were grown by metalorganic chemical vapor deposition for the first time to the best of our knowledge. The structures consist of a 2-,m thick GaN buffer layer, a 2-nm thick In-rich InGaN single quantum well, and a 20 nm thick GaN capping layer. Single quantum well structures were examined by transmission electron microscopy. Photoluminescence emissions from the single quantum well samples were observed at wavelengths ranged from 400 nm to 500 nm depending upon the growth conditions of the InN layer. From a simple energy level calculation, we found the possibility of extremely large emission peak shift with well thickness. [source]

    Simultaneous optical coherent control of excitonic and biexcitonic polarization in a ZnSe quantum well

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2003
    Tobias Voss
    Abstract The optical coherent-control technique is used to study biexcitonic effects in the four-wave-mixing signal of a ZnSe single quantum well. The signal is analyzed in both directions 2k1 , k2 and 2k2 , k1 which are not equivalent if a pulse pair is applied from direction k1 to achieve coherent control of the induced polarization. It is shown that the coherent control enables a selective enhancement or suppression of the contribution at the exciton and biexciton resonance to the signal, respectively, but only for certain sequences of the excitation pulses. Further, the suppression of exciton-biexciton beats in the signal as a function of tdel by a selective destruction of the biexciton polarization is demonstrated. [source]