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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1487-1492 
    ISSN: 0392-6737
    Keywords: III-V semiconductors ; Electron states in low-dimensional structures (including, quantum wells, superlattices, layer structures, and intercalation compounds) ; Excitons and related phenomena (including electron-hole drops) ; Brillouin and Rayleigh scattering ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A detailed study of the relative role played by localized and/or propagating intermediate excitonic states in, resonant Rayleigh scattering (RRS) is presented for a large set of GaAs quantum well (QW) and bulk structures. We show that the two kinds of states contribute to RRS through different mechanisms. We concluded that RRS occurs via localized states in QW heterostructures, very likely due to localization by the interface roughness, while bulk, crystals turn out to be better candidates for RRS via propagating states.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1383-1387 
    ISSN: 0392-6737
    Keywords: III–V semiconductors ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Excitons and related phenomena (including electron-hole drops) ; III–V compounds and systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We report an experimental study on a large set of InGaAs/GaAs quantum well structures by means of continuous-wave photoluminescence and photoluminescence excitation. The luminescence spectrum at low temperature systematically exhibits a doublet structure whose lineshape is very sensitive to the excitation energy. Accordingly, the excitation spectra detected by monitoring the emission at the two different luminescence peaks have very different profiles, with peaks and/or dips which are not directly related to absorption resonances. As a matter of fact, the anomalies disappear when increasing the temperature or when using an optical bias with energy above the GaAs energy gap. In these cases, the excitation profiles recover the behaviour typical of 2D systems.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0392-6737
    Keywords: Photoluminescence ; Excitons and related phenomena ; Charge carriers: generation, recombination, lifetime and trapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Si presenta, in questo lavoro, uno studio sperimentale degli effetti delle disomogeneità spaziali e temporali nei plasmi di elettroni e lacune generati da impulsi laser potenti in strutture a buche quantiche di GaAs/AlGaAs. Si trova che tali disomogeneità modificano fortemente gli spettri di fotoluminescenza e devono quindi essere considerate per una corretta interpretazione dei dati sperimentali. La forma di riga degli spettri di luminescenza viene analizzata mediante un modello statistico che include, in modo semplice, le disomogeneità spaziali e temporali degli impulsi laser usati per l’eccitazione. Si ottiene un accordo soddisfacente con i dati sperimentali e si trova che i valori dei parametri ottenuti dal fit dipendono in modo sensibile dal modello assunto per la descrizione delle disomogeneità. Grande cautela deve essere quindi usata nel dedurre le proprietà del plasma fotogenerato a partire da una analisi delle forme di riga.
    Notes: Summary The effects on the luminescence lineshape of the spatial and temporal inhomogeneities of the electron-hole plasma generated by strong laser pulses in GaAs/AlGaAs multiple quantum well structures are experimentally investigated. It is found that inhomogeneities strongly affect the luminescence spectra and must be taken into account for a correct interpretation of the experimental data. The lineshape of the luminescence spectra is analysed using a statistical model that includes, in a simple way, the spatial and temporal inhomogeneities of the laser pulses used for excitation. A fair agreement is obtained with the experimental data; at the same time the values of the fit parameters turn out to be rather sensitive to the model assumed for describing the inhomogeneities. Therefore, caution has to be used when inferring plasma properties, such as the carrier density and temperature, from a lineshape analysis.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physica B: Physics of Condensed Matter 170 (1991), S. 561-565 
    ISSN: 0921-4526
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Chemical Physics Letters 220 (1994), S. 14-18 
    ISSN: 0009-2614
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3011-3016 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A large set of InGaAs/GaAs quantum well structures was investigated by means of continuous wave photoluminescence (PL) and photoluminescence excitation spectroscopy. Strong photomodulation effects are observed in PL, namely, a strong sensitivity to the excitation energy and strong changes in the line shape when resonant and nonresonant excitations are used together. Correspondingly, the exciton emission exhibits a doublet structure and the excitation spectra, as detected by monitoring the emission at the two peak energies of the PL doublet, show quite different profiles, with peaks and/or dips not directly related to absorption resonances. On the grounds of time-resolved experiments it is shown that band-bending modifications, due to trapping of free carriers at interface defects, account for the observed photomodulation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The tunneling mechanism of electrons and holes to surface states from near-surface Al0.3Ga0.7As/GaAs quantum wells has been investigated by steady-state and time-resolved photoluminescence spectroscopy, near liquid-helium temperature, of the excitonic e1-hh1 transition in the well. The ensemble of the data, taken over a wide range of optical excitation levels, for various values of the tunneling-barrier thickness, and before and after passivation of the surface by hydrogen, allows a description both of the details of the tunneling mechanism and of the character and behavior of relevant surface states. The main results are summarized as follows: (i) steady-state tunneling is ambipolar, namely, separate for electrons and holes, rather than excitonic; (ii) Spicer's advanced unified defect model for an oxidized GaAs surface, antisite-As donors as dominating surface traps, provides an appropriate description of the state distribution at the interface between AlGaAs and its oxide; (iii) hole accumulation in surface states, resulting from the nominally different unipolar tunneling probability for the two carriers (and increasing with excitation level), generates a dipole electric field across the tunneling barrier, extending into the well; (iv) hydrogenation efficiently passivates electron trapping in surface states, but not hole tunneling and the consequent generation of a surface field by illumination; (v) the experimental findings agree with a model for ambipolar tunneling based on a self-consistent quantum-mechanical approach.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2809-2812 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence and photoluminescence excitation spectra have been performed on GaAs/AlGaAs quantum well structures in the temperature range 4–300 K. Sharp exciton resonances are present up to room temperature and can be ascribed to localized excitons for T≤50–70 K and to free excitons at higher values of T. Nevertheless, a line-shape analysis of the PL spectra clearly shows the presence of band-to-band recombination. A fit based on a simple statistical model reproduces with high accuracy the photoluminescence spectrum line shape and allows to evaluate the relative densities of excitons and free carriers generated by the exciton dissociation. We find that the ratios of the relative densities can be interpreted on the basis of the law of mass action for describing the thermal equilibrium between excitons, electrons, and holes.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1982-1984 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate the optical properties of InAs self-assembled quantum dots grown on (N11)A/B GaAs substrates, by means of cw photoluminescence under different excitation power densities. We observe a sizeable blue-shift of photoluminescence band induced by increasing the photogenerated carrier density. The shift depends on the substrate orientation and exhibits a strong asymmetric dependence on the substrate termination. We attribute the photoluminescence blue-shift to a reverse quantum confined Stark shift of ground state transition energies in the quantum dots. This effect arises from the photogenerated charge screening of the built-in piezoelectric field present in such strained structures grown on high index planes. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 931-933 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a detailed investigation of the carrier dynamics in a set of InAs/GaAs (N11) quantum dots (QD) by means of time-resolved photoluminesce (PL) techniques. A dynamical red shift of the PL bands when increasing the delay time after the pulse excitation is observed. We attribute this intrinsic optical nonlinearity to the photoinduced screening of internal built-in electric field. The value of the redshift of the QD emission band decays with the carrier population demonstrating the intrinsic nature of the built-in field. Its dependence on the substrate orientation and termination agrees with the expected piezoelectric induced quantum confined Stark effects of the QD optical transitions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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