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  • 1
    Electronic Resource
    Electronic Resource
    Precipitation on a Dislocation (1959)
    [s.l.] : Nature Publishing Group
    Nature 183 (1959), S. 34-35 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A possible mechanism for the growth of the precipitates is suggested by the observation that these are discrete and lie along the dislocation lines, that is, the impurities migrate to the dislocation and then flow rapidly down the core to sites where precipitates have nucleated. Such a possibility ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/183034a0
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  • 2
    Electronic Resource
    Electronic Resource
    Assessment of oxygen in gallium arsenide by infrared local vibrational mode spectroscopy (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1442-1444 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two infrared local vibrational mode (LVM) absorption lines occurring at 715 and 845 cm−1 shift to 679 and 802 cm−1 in gallium arsenide doped with 18O, proving that the lines arise from the vibrations of oxygen impurities. The 715 cm−1 line exhibits a triplet 69,71Ga isotope fine structure consistent with that expected from a quasi-substitional VAs-O center. The 845 cm−1 line appears as a closely spaced doublet expected for a bonded interstitial oxygen atom.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100691
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  • 3
    Electronic Resource
    Electronic Resource
    Spatial Orientation in the Blind (1967)
    [s.l.] : Nature Publishing Group
    Nature 215 (1967), S. 1413-1414 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] One test of spatial orientation is to ask subjects to move through an unfamiliar environment by means of a map. Tactual maps in particular have been employed in clinical tests for spatial orientation during the past decade (page 270 of ref. 2 gives a summary). We have been carrying out work with a ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2151413a0
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  • 4
    Electronic Resource
    Electronic Resource
    Silicon incorporation in GaAs: From delta-doping to monolayer insertion (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2431-2434 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Raman spectroscopy was used to study the incorporation of Si into doping layers in GaAs, grown by molecular beam epitaxy at a temperature of 400 °C, for Si concentrations ranging from the δ-doping level to a ML coverage. The strength of the scattering by local vibrational modes of substitutional Si was almost constant for Si areal concentration [Si]A in the range 5×1012〈[Si]A〈5×1013 cm−2 but then decreased, dropping below the detection limit for [Si]A(approximately-greater-than)3×1014 cm−2. At these concentrations a new vibrational band emerged at a frequency close to 470 cm−1 and developed into the optic zone center phonon of a coherently strained epitaxial layer of Si embedded in GaAs when a coverage of ≈1.5 ML (9.3×1014 cm−2) was reached. These findings strongly indicate that the observed saturation and the eventual decrease of the concentration of substitutional silicon is caused by an increasing incorporation of deposited Si into two-dimensional islands of covalently bonded Si. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360165
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  • 5
    Electronic Resource
    Electronic Resource
    Oxygen loss during thermal donor formation in Czochralski silicon: New insights into oxygen diffusion mechanisms (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1427-1442 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: As-grown Czochralski silicon samples with different oxygen concentrations have been heated at temperatures in the range 350–500 °C. Oxygen loss during anneals at low temperatures (T≤400 °C) is shown to follow second-order kinetics and measurements led to values of oxygen diffusivity that were larger than normal by a factor of ∼3, assuming the capture radius for dimer formation was 5 A(ring). Variations in the rate of [Oi] loss during more extended anneals could be explained if oxygen diffusion was initially enhanced but tended to its normal value as the anneals progressed. Much greater initial enhancements were derived from similar measurements for samples which had been hydrogenated by a heat treatment in H2 gas at 1300 °C for 30 min followed by a rapid quench to room temperature, and the enhancements were consistent with values derived from measurements of the relaxation of stress-induced dichroism. At higher temperatures (T≥450 °C) the measured rates of [Oi] loss were less than the expected rate of Oi-Oi interaction and tended to vary with increasingly high powers of [Oi]. Modeling of the clustering process demonstrated that the reductions could be explained if the oxygen dimers were present in a quasiequilibrium concentration throughout the anneals. The establishment of this equilibrium appears to require that oxygen dimers diffuse much more rapidly than isolated Oi atoms. The kinetics of oxygen loss over the whole range of temperatures can then be explained if dimer clustering leads mainly to increases in concentrations of agglomorates containing large numbers (≥8) of oxygen atoms. It is therefore possible to account for thermal donor (TD) formation based on the formation of different sizes of oxygen clusters, although the possibility that self-interstitials are involved in TD formation is not excluded. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358890
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  • 6
    Electronic Resource
    Electronic Resource
    The infrared vibrational absorption spectrum of the Si–X defect present in heavily Si doped GaAs (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 137-141 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heavily silicon doped GaAs grown by molecular beam epitaxy using a single gallium isotope source (69Ga) has been studied by infrared absorption to reveal localized vibrational modes (LVMs) of Si complexes. The structure observed close to 367 cm−1 is the same as that present in normal GaAs:Si spectra and does not result from mixed Ga isotopes. The electron trap Si–X gives three LVMs at 368.4, 370.0, and 399.6 cm−1, typical of second neighbor donor-acceptor pairs, but inconsistent with a previous proposal that its structure is the planar defect VGa–SiAs–AsGa. It is now suggested that the defect is a perturbed SiGa–VGa center, involving a second Si atom or a second vacancy. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365791
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  • 7
    Electronic Resource
    Electronic Resource
    Aligned carbon–hydrogen complexes in GaAs formed by the decomposition of trimethylgallium during metalorganic vapor phase epitaxy and atomic layer epitaxy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 7255-7260 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Highly carbon doped (001) oriented GaAs layers were grown by metalorganic vapor phase epitaxy using the precursor trimethylgallium with either arsine or trimethylarsenic. Postgrowth infrared measurements using polarized light demonstrate that proposed grown-in planar carbon–hydrogen [H–(CAs)2] complexes, giving vibrational absorption at 2688 cm−1, have the two CAs atoms aligned along the [110] direction. A previously unreported absorption peak at 576 cm−1 exhibits polarization dependent absorption orthogonal to that of the 2688 cm−1 line. Investigation of a sample containing the [D–(CAs)2] complex indicates that the 576 cm−1 line would have to be a transverse mode of the unpaired CAs atom. Polarization difference spectra show the presence of other aligned carbon related complexes giving absorption close to the line (582 cm−1) due to isolated CAs atoms. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365352
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  • 8
    Electronic Resource
    Electronic Resource
    The bonding of CAs acceptors in InxGa1−xAs grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6754-6760 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: InxGa1−xAs layers (0≤x≤0.37) doped with carbon (〉1020 cm−3) were grown on semi-insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAs for values of x up to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest-neighbor bonding configurations of CAs were investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A−1 symmetry) and the symmetric XH mode (A+1 symmetry) of the H–CAs pairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm−1 had been assigned to passivated Ga4CAs clusters. New modes at 2550 and 430 cm−1 increased in strength with increasing values of x and are assigned to passivated InGa3CAs clusters. These results were compared with ab initio local density functional theory. Modes due to AlInGaCAs clusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4 is an efficient C doping source since both In–CAs bonds as well as Ga–CAs bonds are formed, whereas there is no evidence for the formation of In–CAs bonds in samples doped with C derived from trimethylgallium or solid sources. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363803
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  • 9
    Electronic Resource
    Electronic Resource
    Native defects in low-temperature GaAs and the effect of hydrogenation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 2411-2422 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A range of experimental techniques has been used to measure point defect concentrations in GaAs layers grown at low temperatures (250 °C) by molecular-beam epitaxy (LT-GaAs). The effects of doping on these concentrations has been investigated by studying samples containing shallow acceptors (Be) or shallow donors (Si) in concentrations of ∼1019 cm−3. Material grown under As-rich conditions and doped with Be was completely compensated and the simultaneous detection of As0Ga by near-band-edge infrared absorption and As+Ga by electron paramagnetic resonance confirmed that the Fermi level was near the midgap position and that compensation was partly related to AsGa defects. There was no evidence for the incorporation of VGa in this layer from positron annihilation measurements. For LT-GaAs grown under As-rich conditions and doped with Si, more than 80% of the donors were compensated and the detection of SiGa–VGa pairs by infrared localized vibrational mode (LVM) spectroscopy indicated that compensating VGa defects were at least partly responsible. The presence of vacancy defects was confirmed by positron annihilation measurements. Increasing the Si doping level suppressed the incorporation of AsGa. Exposure of the Be-doped layer to a radio-frequency hydrogen plasma, generated a LVM at 1997 cm−1 and it is proposed that this line is a stretch mode of a AsGa–H–VAs defect complex. For the Si-doped layer, two stretch modes at 1764 and 1773 cm−1 and a wag mode at 779 cm−1 relating to a H-defect complex were detected and we argue that the complex could be a passivated As antisite. The detection of characteristic hydrogen-native defect LVMs may provide a new method for the identification of intrinsic defects. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360163
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  • 10
    Electronic Resource
    Electronic Resource
    The transition from dilute aluminum δ structures to an AlAs monolayer in GaAs and a comparison with Si δ doping (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 7627-7629 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superlattices of Al δ layers embedded in GaAs have been grown by molecular beam epitaxy at 400 °C on (001) GaAs. Infrared absorption measurements revealed a shift of the Al localized vibrational mode (LVM) from 361.4 to 358.3 cm−1 as the doping was increased from 0.25 monolayers (ML) to 1.4 ML per δ plane, while Raman scattering demonstrated a clear transition from the TO-like LVM to a longitudinal LO-like mode. X-ray measurements showed that the Al atoms were confined to a thickness of 6 A(ring) for the highest areal concentrations. The LVM behavior is compared with that of Si δ layers where the absorption tends to zero as the areal concentration increases up to 0.5 ML. It is concluded that SiGa atoms move off their lattice sites and/or change their charge states as the coverage approaches 0.5 ML. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357931
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