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  • 1
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2996-2998 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: High-pressure, low-temperature photoluminescence spectra of Si-doped GaAs grown by molecular-beam epitaxy show well-defined features corresponding to nitrogen-bound exciton recombination, together with other isoelectronic center-bound excitonlike lines. Though N, when isolated, only influence weakly the GaAs electronic properties, we briefly discuss the consequences of its association with other impurities. It is suggested that complexes involving isovalent impurities may be responsible for part of the defect bound exciton luminescence, observed by several authors in molecular-beam-epitaxy–grown GaAs. The source of isovalent impurities is tentatively attributed to the high-temperature boron nitride crucibles.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3721-3728 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This work discusses the temperature behavior of the various photoluminescence (PL) transitions observed in undoped, n- and p-doped GaN in the 9–300 K range. Samples grown using different techniques have been assessed. When possible, simple rate equations are used to describe the quenching of the transitions observed, in order to get a better insight on the mechanism involved. In undoped GaN, the temperature dependence of band edge excitonic lines is well described by assuming that the A exciton population is the leading term in the 50–300 K range. The activation energy for free exciton luminescence quenching is of the order of the A rydberg, suggesting that free hole release leads to nonradiative recombination. In slightly p-doped samples, the luminescence is dominated by acceptor related transitions, whose intensity is shown to be governed by free hole release. For high Mg doping, the luminescence at room temperature is dominated by blue PL in the 2.8–2.9 eV range, whose quenching activation energy is in the 60–80 meV range. We also discuss the temperature dependence of PL transitions near 3.4 eV, related to extended structural defects. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 183-187 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: GaN epilayers and GaN/AlGaN quantum wells (QWs) were grown by molecular beam epitaxy on GaN(0001) single crystal substrates. Transmission electron microscopy (TEM) was used to assess the crystal quality of the homoepitaxial layers. A dislocation density of less than 105 cm−2 is deduced from TEM imaging. Low temperature (1.8 K) photoluminescence (PL) of homoepitaxial GaN reveals PL linewidths as low as 0.3 meV for bound excitons. The PL integrated intensity variation between 10 and 300 K is compared to that observed on a typical heteroepitaxial GaN/Al2O3 layer. A 2 nm thick GaN/Al0.1Ga0.9N QW has been studied by time-resolved and continuous wave PL. The decay time is close to a purely radiative decay, as expected for a low defect density. Finally, the built-in polarization field measured in a homoepitaxial QW is shown to be comparable to that measured on heteroepitaxial QWs grown either on sapphire or silicon substrates. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 806-810 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: X-ray photoelectron spectroscopy has been performed in order to investigate the effects of the chemical etching of GaAs {001} surfaces by the H2SO4/H2O2/H2O solution used following the procedure currently practiced in the molecular-beam-epitaxy technique. It is demonstrated that, in contrast to what is generally believed, rinsing in running deionized water after etching does not produce any passivating oxide film on the surface. The surface-oxidized phases are only due to the sample manipulation in air after etching. This oxidation process is enhanced by the sample heating for indium soldering on the sample holder. It is shown that the surface-oxidized phases can be avoided by handling the sample under an inert atmosphere. Results of thermal desorption of the surface-oxidized phases are also given.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 3714-3720 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: AlGaN/GaN quantum well (QW) structures are grown on c-plane sapphire substrates by molecular beam epitaxy. Control at the monolayer scale of the well thickness is achieved and sharp QW interfaces are demonstrated by the low photoluminescence linewidth. The QW transition energy as a function of the well width evidences a quantum-confined Stark effect due to the presence of a strong built-in electric field. Its origin is discussed in terms of piezoelectricity and spontaneous polarization. Its magnitude versus the Al mole fraction is determined. The role of the sample structure geometry on the electric field is exemplified by changing the thickness of the AlGaN barriers in multiple-QW structures. Straightforward electrostatic arguments well account for the overall trends of the electric-field variations. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2111-2113 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The insertion of few AlAs monolayers at the interfaces between a GaAs quantum well and (Al,Ga)As barriers gives rise to a new type of structure which is well described as a double-barrier quantum well. It is shown that only one or two AlAs monolayers are sufficient to significantly increase the confinement energies. Our results are discussed in the light of low-temperature photoluminescence experiments and are well described in the framework of numerical calculations based on the envelope function formalism.
    Materialart: Digitale Medien
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  • 7
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: An ultrahigh-vacuum compatible four-circle diffractometer coupled to a molecular-beam epitaxy growth chamber has been designed to collect grazing-incidence x-ray diffraction (GIXD) spectra on in situ grown III-V semiconductor surfaces and interfaces. The unit is on line at the D25 bending magnet beam port of the LURE-DCI hard x-ray synchrotron-radiation facility (Orsay, France). Epilayer growth, surface processing, and diffraction data collection are performed without interruption of the ultrahigh-vacuum environment (in the low 10−10-mbar range) around the sample. The setup has been first applied to the determination of the atomic structures of GaAs(001) reconstructed surfaces. Results concerning the As-saturated c(4×4) phase are presented together with preliminary information on the As-stabilized 2×4 reconstruction.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 237-243 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Auger electron spectroscopy (AES) and electron loss spectroscopy (ELS) have been performed in order to investigate vacuum annealing effects on InP surface. Both techniques appeared suitable for detecting indium clustering induced by thermal surface decomposition through InM4.5N4.5N4.5 spectrum modifications (AES) and In plasmon excitation (ELS). The formation of In microinclusions at the surface is detected by the two techniques for annealing temperature of 460±30 °C. In addition, AES shows that phosphorus has a complex behavior near the surface involving diffusion from the bulk, surface segregation, and desorption. These competitive mechanisms are shown to result in phosphorus enrichment or depletion of the surface layer depending mainly on the annealing temperature.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ag/Fe, Ag/Cr, and Fe/Cr superlattices grown on GaAs (001) by molecular-beam epitaxy are compared on the basis of their structural properties. Highly ordered superlattices with very sharp interfaces are obtained for Ag-based structures (Ag/Fe, Ag/Cr). Although several attempts have been made to improve the growth process of Fe/Cr superlattices, they are far from being so well defined. This is a consequence of a progressive degradation which occurs when the superlattice thickness increases and becomes clearly observable in reflection high-energy electron diffraction above roughly 300 A(ring). However, using an optimum growth temperature, reasonably well-defined structures, suitable for subsequent magnetic studies, are obtained.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2605-2607 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: GaAs/AlxGa1−xAs quantum well and superlattice structures have been grown at 600 °C by molecular beam epitaxy on GaAs (001) substrates exactly oriented or slightly misoriented towards (111) Ga and (111) As. It is shown that for the growth conditions used, the step orientation (nature) has a striking influence on the photoluminescence (PL) features of the grown structures: steps along [1¯10] (Ga-type steps) lead to sharp PL lines (pseudosmooth interfaces), while a considerable broadening of the PL (rough interfaces) is obtained when the steps are along [110] (As-type steps).
    Materialart: Digitale Medien
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