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  • 1
    Electronic Resource
    Electronic Resource
    Influence of substrate temperature on lattice strain field and phase transition in MeV oxygen ion implanted GaAs crystals (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2964-2969 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study of the influence of substrate temperature on the radiation-induced lattice strain field and crystalline-to-amorphous (c–a) phase transition in MeV oxygen ion implanted GaAs crystals has been made using channeling Rutherford backscattering spectroscopy, secondary ion mass spectrometry, and the x-ray rocking curve technique. A comparison has been made between the cases of room temperature (RT) and low temperature (LT) (about 100 K) implantation. A strong in situ dynamic annealing process is found in RT implantation at a moderate beam current, resulting in a uniform positive strain field in the implanted layer. LT implantation introduces a freeze-in effect which impedes the recombination and diffusion of initial radiation-created lattice damage and defects, and in turn drives more efficiently the c–a transition as well as strain saturation and relaxation. The results are interpreted with a spike damage model in which the defect production process is described in terms of the competition between defect generation by nuclear spikes and defect diffusion and recombination stimulated by electronic spikes. It is also suggested that the excess population of vacancies and their complexes is responsible for lattice spacing expansion in ion-implanted GaAs crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348608
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  • 2
    Electronic Resource
    Electronic Resource
    MeV oxygen ion implantation induced compositional intermixing in AlAs/GaAs superlattices (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 896-898 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present in this letter an investigation of compositional intermixing in AlAs/GaAs superlattices induced by 2 MeV oxygen ion implantation. The results are compared with implantation at 500 keV. In addition to Al intermixing in the direct lattice damage region by nuclear collision spikes, as is normally present in low-energy ion implantation, Al interdiffusion has also been found to take place in the subsurface region where MeV ion induced electronic spike damage dominates and a uniform strain field builds up due to defect generation and diffusion. Uniform compositional intermixing of the superlattices results after subsequent thermal annealing when Al interdiffusion is stimulated through recovery of the implantation-induced lattice strain field, the reconstruction and the redistribution of lattice defects, and annealing of lattice damage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103397
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  • 3
    Electronic Resource
    Electronic Resource
    Mixing inhibition and crystalline defects in heavily Si-doped AlAs/GaAs superlattices (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 2650-2652 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superlattice mixing in heavily silicon-doped AlAs/GaAs superlattices has been examined by secondary-ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). Samples were grown by molecular beam epitaxy with Si concentrations of 1018 to 1020 cm−3 introduced during the growth process. Interdiffusion of Al was inhibited at a Si concentration of 1020 cm−3. Defect clusters and prismatic dislocation loops were found to be associated with Si concentrations of 1020 and 1019 cm−3, respectively. Si was observed by SIMS to segregate preferentially into the GaAs layers and TEM observation revealed defect formation in these same layers during the diffusion process, suggesting a strong correlation between Si segregation and defect formation. In the range of Si concentrations employed, the Al diffusion coefficient is found to vary as the third power of the estimated electron concentration, consistent with our previous results at lower concentrations. These results suggest that the diffusion inhibition at high Si concentrations may arise from the trapping of mobile Si species by defects with a consequent reduction of the carrier concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100183
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  • 4
    Electronic Resource
    Electronic Resource
    Integrated external cavity GaAs/AlGaAs lasers using selective quantum well disordering (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 540-542 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Integrated external cavity GaAs/AlGaAs single quantum well lasers were fabricated by selective quantum well disordering. Lasers with 2.07-mm-long passive sections and 0.48-mm-long active sections had threshold currents of 33 mA, compared to 9.8 mA for lasers without passive sections. Lasing data indicate a residual modal loss of 11 cm−1 in the passive sections, consistent with direct waveguide loss measurements. Control composite structures with a nondisordered quantum well in the passive sections showed significantly higher threshold currents and a large red shift of as much as 11.4 nm in the lasing wavelength compared to lasers without a passive cavity. This red shift is the main reason for the reduced resonant losses in integrated external cavity lasers with a nondisordered quantum well in the passive section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101848
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  • 5
    Electronic Resource
    Electronic Resource
    InGaAs/InP superlattice mixing induced by Zn or Si diffusion (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1051-1053 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent studies have shown that Zn diffusion preferentially induces mixing (interdiffusion) of In and Ga in unstrained InGaAs/InP superlattices, with little diffusion of the anions. In the present study, a 3.1% lattice mismatch is accommodated in the mixed superlattice with no observable defects in layers on the order of the predicted critical layer thickness. At high concentrations, Zn resides preferentially in the InP layers in the form of Zn3P2. In marked contrast to this behavior of Zn, Si diffusion is observed to cause comparable interdiffusion on the cation and anion sublattices within a narrow range of dopant concentration. This result is at odds with some recent mixing models and is consistent with a divacancy mixing mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100406
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  • 6
    Electronic Resource
    Electronic Resource
    Conversion of InP/In0.53Ga0.47As superlattices to Zn3P2/In1−xGaxAs and Zn3P2/Zn3As2 superlattices by Zn diffusion (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1160-1162 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A standard 600 °C closed-tube Zn diffusion into an unstrained InP/In0.53Ga0.47As superlattice was found to produce new superlattices containing Zn3P2 layers, and in some cases Zn3As2 layers. Crystalline properties and diffusion profiles were examined by transmission electron microscopy and secondary-ion mass spectrometry. Initial doping of Zn enhances the diffusion of In and Ga and results in a superlattice of uniform In and Ga distribution. Upon further infusion of Zn, Zn3P2 forms selectively in the phosphorus layers and propagates from the surface while maintaining an atomically abrupt Zn3P2/In1−xGaxP interface. Zn3As2 conversion is also observed to occur under sufficiently stringent conditions. Diffusion of P and As was not observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101480
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  • 7
    Electronic Resource
    Electronic Resource
    Study of interdiffusion in a Te-doped AlAs-GaAs superlattice (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2165-2167 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The enhanced layer interdiffusion in Te-doped AlAs/GaAs superlattices has been studied by secondary ion mass spectrometry. The superlattice sample was grown by organometallic chemical vapor deposition with Te doping at concentrations of 2×1017–3×1018 cm−3 during the growth process. In the temperature range from 800 to 1000 °C, the Al diffusion coefficient has an activation energy of 3.0 eV and is approximately proportional to the Te concentration. These results contrast sharply with Si-induced mixing which, in an analogous experiment, yielded an activation energy of 4.1 eV for the Al diffusion coefficient with a high power law dependence on the Si concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342848
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  • 8
    Electronic Resource
    Electronic Resource
    Thick films of Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O by solution processes (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6382-6387 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have prepared superconducting thick films of the Bi-based and the Tl-based cuprates via the decomposition of aqueous-glycerol solutions containing the salts of the elements. Preliminary results are presented in this work. The substrates are coated prior to heat treating, either by dipping or by spraying on various substrates heated at 200 °C. Short firing times are required in order to minimize the loss of the constituent Bi (Tl). We find that nitrates of the constituents dissolved in a water-glycerol solution increase the reaction rate in comparison to pure nitrate aqueous solutions. They also help to produce the correct superconducting phase before some reaction with the substrate occurs or too much of the constituent Bi (Tl) is lost during heating to form the superconducting phase. However, the thallium phases cannot be obtained if the films are not fired in the presence of a high pressure of thallium in a sealed capsule. The films are composed of platelets, a few microns large, that are on average oriented parallel to the substrate with their c axis normal. The Bi films show an onset temperature at 85 K and zero resistance at 75 K while the Tl films show an onset temperature of 105 K and zero resistance at 95 K. The critical currents obtained to date are quite low (∼50 A/cm2 at 77 K for the thallium phase).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342075
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  • 9
    Electronic Resource
    Electronic Resource
    Column radioimmunoassay method for the determination of digitoxin (1975)
    s.l. : American Chemical Society
    Analytical chemistry 47 (1975), S. 1583-1586 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac60359a047
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  • 10
    Electronic Resource
    Electronic Resource
    Ge redistribution in solid-phase Ge/Pd/GaAs ohmic contact formation (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 334-339 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A backside secondary ion mass spectrometry technique is employed to examine elemental redistribution in the Ge/Pd/GaAs ohmic contact as a function of annealing conditions. Dilute Al containing marker layers (Ga1−x Alx As) in the GaAs permit precise calibration and alignment of the elemental depth profiles. Double etch-stop thinning yields high depth resolution. The onset of ohmic behavior is found to occur when Ge is detected at the GaAs surface. Good ohmic behavior is observed when an interfacial layer of reacted Pd4GaAs is dispersed and complete coverage of Ge occurs. The Ge/GaAs interface is abrupt with the Ge concentration dropping by over three orders of magnitude within 100 A(ring). About 40 A(ring) of GaAs is found to be consumed during the ohmic contact formation. Degradation of the ohmic contacts, as a result of further heat treatment, was found to correlate with Ge in-diffusion into the GaAs. The results place strict limitations on doping and heterointerface models of ohmic behavior for this contact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345258
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