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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4444-4446 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The stability of an amorphous GexSi1−xO2 in contact with an epitaxial (100)GexSi1−x layer obtained by partially oxidizing an epitaxial GexSi1−x layer on a (100)Si substrate in a wet ambient at 700 °C is investigated for x=0.28 and 0.36 upon annealing in vacuum at 900 °C for 3 h, aging in air at room temperature for 5 months, and immersion in water. After annealing at 900 °C, the oxide remains amorphous and the amount of GeO2 in the oxide stays constant, but some small crystalline precipitates with a lattice constant similar to that of the underlying GeSi layer emerge in the oxide very near the interface for both x. Similar precipitates are also observed after aging for both x. The appearance of these precipitates can be explained by the thermodynamic instability of GexSi1−xO2 in contact with GexSi1−x. In water at RT, 90% of GeO2 in the oxide is dissolved for x=0.36, while the oxide remains conserved for x=0.28.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6674-6678 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The experimental results of a molecular-beam epitaxy grown Si/GeSi p-n heterojunction are reported. It is found that the current flow in these p-n heterojunctions shows a nonideality factor of about 1.5 at room temperature and 2.35 at liquid nitrogen temperature. The nonideal behavior of the Si/GeSi p-n heterojunction is attributed to the charges that are trapped at the heterointerface. Annealing the samples at temperatures higher than the growth temperature results in an increase in the density of defects as well as an increase in the nonideal current. C-V measurements were employed to further investigate the behavior of the charges that are trapped in the interface. From C-V measurements under reverse bias it is found that increasing the annealing time and temperature increases the density of interface traps. In addition, a charge density of about 1012 cm−2 is found to be present at the Si/GeSi interface for the as-grown sample and increases with increasing annealing time and temperature.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4305-4313 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SimGen strained layer superlattice (SLS) structures were grown by molecular beam epitaxy on GexSi1−x buffer layers on 〈100〉 Si substrates to determine the effects of buffer layer composition, SLS thickness ratio, and superlattice periodicity, on the overall quality of these structures. X-ray diffraction methods were used to determine how closely actual periodicities and compositions met targeted values, and to evaluate the quality of these samples. In most instances the as-grown structures matched the targeted values to within 10%, though in some instances deviations of 20–25% in either the period or composition were observed. The quality of the SLS structures was greatly dependent on the composition of the buffer layer on which it was grown. SimGen SLS structures grown on Si- and Ge-rich buffer layers were of much higher quality than SimGem SLSs grown on Ge0.50Si0.50 layers, but the x-ray rocking curves of the SimGen samples indicated that they were far from perfect and contained moderate levels of defects. These results were confirmed by cross sectional transmission electron microscopy, which showed that the SimGem structures contained significant numbers of dislocations and that the layers were nonuniform in thickness and wavy in appearance. SimGen structures, however, displayed fewer defects but some dislocations and nonparallelism of layers were still observed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3626-3627 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Wet thermal oxidation at 1000 °C of a 470-nm-thick epitaxial Ge0.36Si0.64 layer on (100)Si produces oxides of different composition depending on the details of the oxidation procedure. When a cold sample is directly exposed to the hot steam, the surface layer of the oxide contains both Ge and Si. Only SiO2 forms if a preheated sample is exposed to the hot steam. The effect is not present for dry oxidation and is attributed to the known enhancement of the wet oxidation rate by Ge, coupled with the transient warm up of a sample when it is immersed cold in hot steam.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6039-6045 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The damage and strain induced by irradiation of both relaxed and pseudomorphic GexSi1−x films on Si(100) with 100 keV 28Si ions at room temperature have been studied by MeV 4He channeling spectrometry and x-ray double-crystal diffractometry. The ion energy was chosen to confine the major damage to the films. The results are compared with experiments for room temprature Si irradiation of Si(100) and Ge(100). The maximum relative damage created in low-Ge content films studied here (x=10%, 13%, 15%, 20%, and 22%) is considerably higher than the values obtained by interpolating between the results for relative damage in Si-irradiated single crystal Si and Ge. This, together with other facts, indicates that a relatively small fraction of Ge in Si has a significant stabilizing effect on the retained damage generated by room-temperature irradiation with Si ions. The damage induced by irradiation produces positive perpendicular strain in GexSi1−x, which superimposes on the intrinsic positive perpendicular strain of the pseudomorphic or partially relaxed films. In all of the cases studied here, the induced maximum perpendicular strain and the maximum relative damage initially increase slowly with the dose, but start to rise at an accelerated rate above a threshold value of ∼0.15% and 15%, respectively, until the samples are amorphized. The pre-existing pseudomorphic strain in the GexSi1−x film does not significantly influence the maximum relative damage created by Si ion irradiation for all doses and x values. The relationship between the induced maximum perpendicular strain and the maximum relative damage differs from that found in bulk Si(100) and Ge(100).
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectroscopic ellipsometry (SE) characterization of several complex SixGe1−x/Si heterostructures prepared for device fabrication, including structures for heterojunction bipolar transistors (HBT), p- and n-type heterostructure modulation-doped field-effect transistors, has been performed. It is shown that SE can simultaneously determine all active layer thicknesses, SixGe1−x compositions, and the oxide overlayer thickness, with only a general knowledge of the structure topology needed a priori. The characterization of HBT material includes the SE analysis of a SixGe1−x layer deeply buried (600 nm) under the silicon emitter and cap layers. In the SE analysis of n-type heterostructures, a silicon layer under tensile strain was examined. It was found that an excellent fit can be obtained using optical constants of unstrained silicon to represent the strained silicon conduction layer. SE was also used to measure lateral sample homogeneity, providing quantitative identification of the inhomogeneous layer. Surface overlayers resulting from prior sample processing were also detected and measured quantitatively. These results should allow SE to be used extensively as a nondestructive means of characterizing SixGe1−x/Si heterostructures prior to device fabrication and testing.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 1191-1193 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Schottky barrier heights in the epitaxial (100) CoGa/n-(100) GaAs diodes were studied by the I-V and internal photoemission methods. Diodes of these epitaxial contacts were shown to exhibit good rectifying behaviors and the forward current was found to follow the thermionic emission theory. Using the temperature dependence of the barrier heights, we show that the Schottky barrier heights are about 0.67 eV by I-V and 0.68 eV by internal photoemission measurements. The Schottky barrier height was found to be constant for contacting to n-type GaAs in the temperature range between 150 and 300 K. From this fact, we conclude that the metal Fermi level is pinned relatively to the GaAs conduction band minimum in this case. This finding is similar to other epitaxial contacting cases, CoSi2/Si and ErSi2/Si, where the Fermi level pins to the nearest semiconductor band [J. Y. Duboz, P. A. Badoz, F. Arnaud d'Avitaya, and E. Rosenche, Phys. Rev. B 40, 10 607 (1989)].
    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 71 (1992), S. 1383-1387 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The intersubband optical absorption and Stark effect of square and step quantum wells in the presence of applied electric field have been investigated theoretically. By considering the tunneling of photoexcited electrons under the influence of electric field in the quantum well, we obtain a shifted and broadened absorption spectrum from the tunneling of electrons. Such broadening leads to a decrease of absorption coefficient when the applied electric field is increased. For detector application of multiple quantum well devices, if efficient tunneling of the photoexcited electrons is desirable for high responsivity, the sharpness of the absorption peak needs to be compromised. Our results provide insight to this broadening and thus the optimization guideline for detector design.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 1279-1282 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thick Si1−xGex strained alloy layers grown by molecular beam epitaxy (MBE) are investigated using photoluminescence (PL) spectroscopy. Near-band-edge luminescence with well resolved phonon structures is observed for both as-grown and deuterated samples. The low energy broad band frequently encountered in MBE-grown alloy layers is shown to be annihilated by deuteration, giving rise to the no-phonon and phonon-assisted near-band-edge PL peaks. The broad band recovers by annealing at T≥360 °C while the intensity of the near-band-edge luminescence vanishes. Secondary ion mass spectroscopy and the effect of deuterium passivation are used to help locate and assign the defects responsible for the low PL efficiency of MBE-grown thick SiGe layers.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 4015-4018 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: About 500-nm-thick films of Ge0.36Si0.64 and Ge0.28Si0.72 grown epitaxially on (100)Si have been oxidized at 700 °C in wet ambient. A uniform GexSi1−xO2 oxide layer forms with a smooth interface between it and the unoxidized GexSi1−x layer below. The composition and structure of that layer remains unchanged as monitored by backscattering spectrometry or cross-sectional transmission electronic microscopy. The oxide of both samples grows as square root of oxidation duration. The parabolic rate constant increases with the Ge content and is larger than that for wet oxidation of pure Si at the same temperature. The absence of a regime of linear growth at this relatively low temperature indicates a much enhanced linear rate constant.
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