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  • 1
    Electronic Resource
    Electronic Resource
    Accurately determining the composition and thickness of layers in a GaAs/InGaAs superlattice (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1609-1614 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The layer thicknesses and composition of molecular beam epitaxy grown four period 200 A(ring)/100 A(ring) GaAs/InGaAs superlattice structures with nominal indium concentrations of 10%, 15%, and 20% were determined by transmission electron microscopy, Rutherford backscattering spectroscopy, double crystal x-ray diffraction (DXRD), photoreflectance (PR), and photoluminescence (PL). The results show that the indium concentration obtained by DXRD is a little low and that obtained by PR and PL is a little high, and that the discrepancies are larger for the larger indium concentrations. We show that both discrepancies can be accounted for by relaxation of the lattice, elastic relaxation as represented by a radius of curvature, and/or plastic deformation as represented by mismatch of dislocations. For the case of elastic relaxation the tetragonal distortion is less than it would be if the sample were perfectly pseudomorphic. The fractions by which it is reduced for the 10%, 15%, and 20% samples was 0.91, 0.86, and 0.77 as determined by DXRD and 0.80, 0.78, and 0.85 as determined by PR/PL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358461
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  • 2
    Electronic Resource
    Electronic Resource
    Infrared absorption of Ge epitaxial films on a GaAs substrate (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 7157-7160 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Germanium films were deposited on GaAs (100) substrates with or without an epiready surface oxide at temperatures between room temperature (RT) and 500 °C using an ultrahigh-vacuum e-beam deposition system. The film at 100 °C on a substrate with a surface oxide had a flat absorption curve over the wave-number range investigated, 500–4000 cm−1, with an absorption of less than 10/cm at 1000 cm−1 (10 μm wavelength). Films deposited at RT and 50 °C on substrates with a surface oxide had comparable low absorption, but they contained an absorption peak at 830 cm−1 associated with the Ge—O bonds. Although all three films were amorphous, the films deposited at the lower temperatures were more porous. This enabled oxygen to percolate in from the atmosphere to form the Ge—O bonds. The films deposited at 150 °C and above on substrates with a surface oxide and at 100 °C with the surface oxide removed thermally in situ prior to deposition the Ge films, and the single crystal films deposited at 400 and 500 °C on oxide-free substrates, had strong absorption in the vicinity of the Ge/GaAs interface with the characteristic of two-dimensional free-carrier absorption. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361486
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  • 3
    Electronic Resource
    Electronic Resource
    A materials study of PtTiGePd ohmic contacts to p+-AlGaAs as a function of annealing temperature (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5225-5230 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Elemental diffusion, interfacial microstructure, and phase composition of Pt/Ti/Ge/Pd ohmic contacts to heavily C-doped Al0.26Ga0.74As were investigated at several annealing temperatures. Results of the material analyses were used to explain the previously determined specific contact resistances measured for each thermal treatment. Evidence of interdiffusion and compound formation between AlGaAs and Pd were visible in a Ga rich Pd-Ga-As reaction zone prior to heat treatment. This phase is critical for the formation of Ga vacancies, which upon heating are occupied by in-diffusing Ge. However, as the annealing temperatures are raised to 530 °C and above, As preferentially out diffuses. The As out diffusion, which is critical to the formation of good p-type ohmic contacts by creating vacancies that the amphoteric Ge can occupy, contributed to the creation and development of the two phase TiAs/Pd12Ga2Ge5 interfacial region overlying the AlGaAs substrate. In response to the enhanced As out diffusion at 600 °C, the interfacial region reached completion, that is, it became laterally continuous and compositionally uniform, and the specific contact resistance achieved its minimum value. At higher annealing temperatures ∼650 °C, the electrical measurements degraded in response to intensive chemical diffusion which resulted in the development of a broad, nonuniform multiphased interfacial region, and the Pt contacting layer ceased to be a homogeneous layer with a smooth surface. The As interfacial compounds form at higher temperatures in AlGaAs than in GaAs suggesting that As is more strongly bonded in the AlGaAs. This contributes to the greater temperature stability of the contacts to AlGaAs. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359272
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphorus-31 NMR saturation-transfer measurements in Saccharomyces cerevisiae: characterization of phosphate exchange reactions by iodoacetate and antimycin A inhibition (1987)
    s.l. : American Chemical Society
    Biochemistry 26 (1987), S. 7483-7492 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00397a043
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  • 5
    Electronic Resource
    Electronic Resource
    Optical investigations of ion implant damage in silicon (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 2591-2594 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ion implantation damage in silicon has been studied utilizing a new optical technique (differential reflectometry). It has been demonstrated that differential reflectometry can be used to identify whether an implanted layer is crystalline, damaged crystalline, or amorphous. The intensity of interband transitions can be used to determine the thickness of a damaged crystalline layer over a submerged amorphous layer. Interference effects were utilized to determine the thickness of an amorphous layer. Thus, differential optical reflectance has far-reaching potential for characterizing implanted substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340996
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  • 6
    Electronic Resource
    Electronic Resource
    Shallow ohmic contact to both n- and p-GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 754-756 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A shallow Pd/Ge/Ti/Pt/ohmic contact for both n- and p-GaAs has been investigated. The contacts were rapid thermally annealed in N2 for 15 s at temperatures from 350 to 550 °C. The lowest average specific contact resistances were 4.7×10−7 and 6.4×10−7 Ω cm2 for the n- and p-GaAs, respectively, when the n-GaAs was doped with Si to 2×1018 cm−3 and the p-GaAs was doped with carbon to 5×1019 cm−3. Electrical measurements and Auger depth profiles showed that the contacts were stable as they remained ohmic after an anneal at 300 °C for 20 h for both n- and p-GaAs. The p contact is more stable than the n contact at the higher temperatures where there is more As outdiffusion as determined by Auger depth profiles. Transmission electron microscopy showed that the interfaces between the p-GaAs and the contacts were smooth for both as-grown and annealed samples, and no oxides were detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355248
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  • 7
    Electronic Resource
    Electronic Resource
    Biaxial and uniaxial stress in gallium arsenide on silicon: A linear polarized photoluminescence study (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 369-371 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have observed anisotropic behavior of the polarization of low-temperature photoluminescence from thick gallium arsenide grown on silicon substrates. The identification of the observed transitions was obtained from analysis of the selection rules, the temperature dependence of the feature intensities, and the transition energies. We find that the low-temperature doublet peaks are due to the emissions from two regions of material experiencing two different kinds of stress, one being biaxial and the other uniaxial. The anisotropy is due to the preferential direction created by parallel microcracks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347147
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  • 8
    Electronic Resource
    Electronic Resource
    The microstructure and electrical properties of nonalloyed epitaxial Au-Ge ohmic contacts to n-GaAs (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4773-4780 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The microstructure and electrical properties of nonalloyed epitaxial Au-Ge contacts were studied. Ohmic behavior was obtained after a 3 h anneal at 320 °C with the lowest average contact resistance and specific contact resistivity found to be ∼0.28 Ω mm and ∼7×10−6 Ω cm2, respectively. Localized reactions in the form of islands were observed across the surface of the contact after annealing and were composed of Au, Ge, and As, as determined by secondary ion mass spectroscopy (SIMS) imaging and Auger depth profiling. Back side SIMS profiles indicate deep Ge and Au diffusion into the GaAs substrate in the island regions. Ohmic contact behavior was found to depend upon both the kinetics of the reactions (localized reactions and island growth) and the thermodynamics (substantial diffusion of both Au and Ge) of the system. A model describing the coupled Au and Ge in-diffusion with respect to the GaAs substrate is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352089
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  • 9
    Electronic Resource
    Electronic Resource
    PdGeTiPt Ohmic contacts to p+-AlxGa1−xAs (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 273-275 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ohmic contacts to heavily C-doped AlGaAs were made using PdGeTiPt that had specific contact resistances Rc, as low as 1.7×10−6 Ω cm2 when annealed at 600 °C. The less heavily doped samples annealed at temperatures between 350 and 500 °C were non-Ohmic, and Rc decreased with increasing annealing temperature between 500 and 600 °C. For the more heavily doped samples, Rc decreased with increasing annealing temperature. Rc increased for all samples at annealing temperatures above 600 °C. Rc rose quickly by 102 when the samples were reannealed at 300 °C for 20 h, but remained unchanged with further reannealing for up to 100 h. This behavior is consistent with partial compensation generated by the rapid out-diffusion of Ga at low annealing temperatures and the subsequent in-diffusion of Ge into the Ga vacancies left behind. The lower Rc obtained with the 600 °C anneal can be explained by an increased As out-diffusion and the subsequent in-diffusion of Ge into the As vacancies at the higher annealing temperatures. Interfacial reactions and elemental diffusion of the contacts investigated via transmission electron microscopy and elemental depth profiles obtained by Auger electron spectroscopy are also consistent with this mode. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114780
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of the composition of strained InGaAsP layers on InP substrates using photoreflectance and double-crystal x-ray diffractometry (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2152-2155 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Determining the composition of strained InGaAsP films through measurements of the lattice spacings and band-gap energies (Eg) requires converting the measured values to ones which would correspond to unstrained material. In strained layers the lattice constants perpendicular and parallel to the growth plane can vary significantly from the relaxed value, and the optically measured Eg is affected by a strain-induced splitting of the valence band and a shifting of the direct gap energy. By combining double-crystal x-ray data with room-temperature photoreflectance results, we determine the InGaAsP composition accurately using an iterative procedure. Film compositions calculated using strain adjusted values of Eg agree with those determined by energy dispersive spectroscopy to within 1–2 at. %, whereas if energy shifts are not considered, the error approaches 10 at. % for strain on the order of 0.4%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349452
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