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  • 11
    Electronic Resource
    Electronic Resource
    Redistribution of Zn in GaAs-AlGaAs heterojunction bipolar transistor structures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 1251-1253 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The redistribution of Zn in the base region of GaAs-AlGaAs heterojunction bipolar transistor structures during growth by organometallic vapor phase epitaxy has been examined with respect to the presence of Si doping in the emitter-contact, emitter, and collector/subcollector layers, and as a function of Zn doping concentration and Si counterdoping level in the p+ base. For a growth temperature of 675 °C the Zn shows no significant redistribution up to concentrations of 3×1019 cm−3 without Si doping. The addition of Si to the adjacent AlGaAs emitter and collector/subcollector layers causes substantial diffusion of Zn from the base, while Si doping of the GaAs emitter contact results in even greater Zn redistribution. Under these conditions, the Zn concentration in the base attains a maximum value of ∼7×1018 cm−3. Silicon counterdoping in the base region retards the Zn diffusion, while strain introduced by an InGaAs cap layer has no effect on the Zn redistribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102528
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  • 12
    Electronic Resource
    Electronic Resource
    Role of vanadium in organometallic vapor phase epitaxy grown GaAs (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1772-1774 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical and photoluminescent properties of vanadium incorporated into GaAs epitaxial layers from a VO(OC2H5)3 source during organometallic vapor phase epitaxy were examined. The vanadium concentration in the GaAs was controllably varied from 1016 to 1018 atoms cm−3. Deep level transient spectroscopy showed the presence of an electron trap at Ec−0.15 eV which increased in concentration with vanadium content of the epitaxial layers. A maximum value of 8×1015 cm−3 for this trap was obtained. There were no midgap electron traps associated with vanadium. In intentionally Si-doped epitaxial layers, co-doping with vanadium was observed to have no effect in reducing the carrier density when the Si concentration was ≥4×1016 cm−3. The net carrier concentration profiles resulting from 29Si implantation into GaAs containing 1018 cm−3 of total V had sharper tails than for similar implantation into undoped material, indicating the presence of less than 1016 cm−3 V-related acceptors. Photoluminescent spectra exhibited the characteristic V+3 intracenter emission at 0.65–0.75 eV. No other deep level photoluminescence was detected. For a V concentration of 1016 cm−3 only 2.5×1013 cm−3 was electrically active. Over the entire V concentration investigated this impurity was predominantly (≥99%) inactive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101287
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  • 13
    Electronic Resource
    Electronic Resource
    Growth of high quality AlGaAs by metalorganic molecular beam epitaxy using trimethylamine alane (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2654-2656 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlGaAs grown by metalorganic molecular beam epitaxy (MOMBE) has been problematic due to oxygen and carbon contamination, particularly when triethylaluminum (TEAl) has been used as the aluminum source. Consequently, we have investigated trimethylamine alane (TMAAl) as a potential replacement for the conventional metalorganic Al sources. AlGaAs films with excellent structural and optical properties have been grown with this source. Photoluminescence intensities from AlGaAs grown by MOMBE at 500 °C using TMAAl are comparable to those from material grown by metalorganic chemical vapor deposition at 675 °C using triethylaluminum (TMAl). Carbon and oxygen levels in MOMBE-grown AlGaAs are drastically reduced in comparison to similar films grown with TEAl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102866
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  • 14
    Electronic Resource
    Electronic Resource
    Mechanisms of interdiffusion in copper/nickel thin-film couples (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 1147-1155 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Mechanisms of interdiffusion in copper/nickel thin-film couples have been investigated in the temperature interval 573–777 K by in situ measurement of contact resistance, Auger depth profiling (ADP), and transmission electron microscopy. Correlation between evolution of contact resistance and measured Auger concentration profiles has been established and mechanisms incorporating rapid grain boundary diffusion, followed by defect-assisted diffusion into grain interiors (Type B kinetics), are proposed to explain the accelerated reactions observed. A modified Whipple model and two independent methods, based on ADP and contact resistance measurements, are used to calculate grain boundary and intragranular diffusion coefficients, respectively. The calculated grain boundary diffusion coefficient is (0.82 cm2/s) exp(−1.48eV/kT) for nickel in copper, and approximately 4×10−13 cm2/s for copper in nickel at 673 K. An average intragranular diffusion coefficient for nickel in copper is determined to be (2.6×10−6 cm2/s) exp(−1.38 eV/kT) by both methods, whereas ADP data yield a corresponding value of (5.2×10−8 cm2/s) exp(−1.51eV/kT) for copper in nickel. It is concluded that characterization of chemical composition and microstructure, combined with in situ measurement of concomitant electrical properties, provides a reliable description of interdiffusion mechanisms in this system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336552
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  • 15
    Electronic Resource
    Electronic Resource
    An analysis of dislocation reduction by impurity hardening in the liquid-encapsulated Czochralski growth of 〈111〉 InP (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4383-4389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Excessive impurity additions have been widely used to suppress dislocation generation in the liquid-encapsulated Czochralski (LEC) growth of InP. We have analyzed this approach by means of the quasi-steady-state heat transfer/thermal stress model. A strong motivation for the investigation was provided by the recent measurement of the critical resolved shear stress σCRS of InP as a function of temperature in the range 748–948 °K for several Ge and S concentrations. The experimental data were analyzed by the method of least squares via the usually accepted logarithmic dependence of σCRS on reciprocal temperature. The extrapolated values of σCRS exhibit a monotonic increase with impurity addition at temperatures near the melting point. Introducing the σCRS and realistic estimates of other physical properties (thermal diffusivity, thermal expansion coefficient, elastic constants, etc.) in the thermal stress model, the dislocation distribution pattern in a {111} substrate cut from a 〈111〉 boule was constructed. This necessitated a suitable recasting of the formalism that was previously applicable only to the {100} orientation. The computed dislocation contour maps on {111} wafers display sixfold symmetry resembling the "Star of David,'' in overall agreement with etch-pit patterns. InP crystals 2.5 cm in diameter grown in a standard high ambient temperature gradient but containing a large amount of Ge ((approximately-equal-to)1019 cm−3) are predicted and observed to be dislocation-free. On the other hand, in nominally undoped material a large density of defects is forecast, especially at the periphery, in line with the etchpit configuration. Intermediate doping levels (∼1017 cm−3 Ge, ∼1018 cm−3 S) reduce the density in the core but leave the outer edge essentially unaltered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335528
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  • 16
    Electronic Resource
    Electronic Resource
    Surface polygonization on GaAs wafers (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1468-1471 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polygonized surface structure produced by furnace annealing GaAs wafers was studied by optical and scanning electron microscopy. The surface structure was revealed by chemically etching wafers which had been implanted with silicon and subjected to a furnace annealing cycle. Cathodoluminescence micrographs demonstrate an absence of impurity segregation to the polygon boundaries. No correlation was found between growth-induced dislocations and the polygonal networks. It is proposed that the surface structure results from a vacancy-condensation process. Related surface effects were observed for rapidly annealed wafers. A correlation between the furnace annealed and rapidly annealed GaAs is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341819
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  • 17
    Electronic Resource
    Electronic Resource
    Residual oxygen levels in AlGaAs/GaAs quantum-well laser structures: Effects of Si and Be doping and substrate misorientation (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 3270-3272 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Oxygen forms nonradiative recombination centers in GaAs and AlGaAs, and is a common contaminant in AlGaAs, irrespective of the growth technique. We find that O tends to accumulate near the GaAs active region of an AlGaAs/GaAs quantum-well laser prepared by molecular beam epitaxy. Moreover, the Be-doped Al0.6Ga0.4As cladding layer has a higher O content than its Si-doped counterpart. We present evidence that Si-doping suppresses, and Be doping favors incorporation of O in AlGaAs. In undoped and Si-doped AlGaAs, the incorporation of O is further reduced by tilting the (100) GaAs substrates towards 〈111〉A. We propose that Be forms stable Be-O complexes in AlGaAs, and thus, there is virtually no desorption of incorporated O. But in Si-doped AlGaAs, O content is reduced due to reaction between group III suboxides and Si, resulting in the formation and desorption of volatile SiO (g). The study suggests that Be doping should be avoided in the p-side of the GRIN region of a laser structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105727
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  • 18
    Electronic Resource
    Electronic Resource
    Thermodynamic interpretation of quaternary (InGaAsP) layer uniformity grown by low-pressure metalorganic vapor phase epitaxy (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 360-362 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: According to a recent study, the compositional nonuniformity for group V sites of quaternary (Q) In0.68Ga0.32As0.7P0.3 layers (λ=1.35 μm) grown by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE) on 50 mm diam InP wafers was reduced from 3% to 1% when tertiary butyl phosphine (TBP)+AsH3 instead of PH3+AsH3 or TBP+tertiary butyl arsine (TBAs) were employed. In this letter we offer a thermodynamic interpretation of these observations. Under LP-MOVPE conditions at a total pressure of 0.08 atm for fully decomposed group V precursors diluted with H2, we show that while the dominant species are the tetramers, the concentration of the dimers is significant and becomes more prominent with rising temperature (T). Examining the [As/P] ratio in the gas phase as a function of reciprocal T, we demonstrate that in the MOVPE range (900–950 K) the slope of these curves changes from steep to moderate and then nearly flat for the sources AsH3+PH3, TBAs+TBP, and AsH3+TBP, respectively. The insensitivity of the [As/P] ratio to the ∼30 K gradient over the susceptor when combining AsH3 and TBP suggests a very effective method to assure compositional uniformity in Q layers prepared by LP-MOVPE. Uniformity results for atmospheric pressure MOVPE employing AsH3 and PH3 are also consistent with the thermodynamic argument.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108956
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  • 19
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of mononuclear and dinuclear bis(2,2'-bipyridine)ruthenium(II) complexes containing sulfur-donor ligands (1989)
    s.l. : American Chemical Society
    Inorganic chemistry 28 (1989), S. 912-920 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00304a023
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  • 20
    Electronic Resource
    Electronic Resource
    U. S. A. (1935)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of personality 4 (1935), S. 0 
    Details
    ISSN: 1467-6494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Psychology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1467-6494.1935.tb02118.x
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