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  • 1990-1994  (9)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    As precipitate redistribution in Si δ-doped low-temperature GaAs (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 5697-5701 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A high-resolution x-ray diffractometer and transmission electron microscope (TEM) are used to characterize the redistribution of As precipitates in Si δ-doped GaAs grown by molecular-beam epitaxy at low substrate temperature (230 °C). The analysis results indicate that superlattice satellite peaks, as observed for samples annealed at 700–900 °C for 10 min, are attributed to the formation of the GaAs/As superlattice. Also, the intensity of satellite peaks in x-ray rocking curves and TEM observations reveals the varying degree of As precipitates confined on the Si δ-doped planes. Furthermore, the asymmetry of the satellite peaks clearly indicates the lattice expansion and contraction of the annealed low-temperature epitaxial layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357076
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Flat band current-voltage-temperature method for band-discontinuity determination and its application to strained InxGa1−xAs/In0.52Al0.48As heterostructures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2893-2903 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A method that combines capacitance-voltage and current-voltage-temperature measurements of a n+-i-n− (or p+-i-p−) heterobarrier structure for reliable determination of the band discontinuity is described. Experimental and analytical procedures for the extraction of the Fermi energies in the doped layers, the location of the flat band condition, and the determination of the barrier height at flat band are given. The effects of nonparabolicity and strain are also considered. Some potential sources of errors encountered in the conventional procedure that is based on the barrier height at zero bias are avoided in this flat band method. The application of this method and other experimental considerations are illustrated by using the strained InxGa1−xAs/In0.52Al0.48As heterointerface as a specific example. The results show that the conduction-band offset ratio, Qc, is nearly constant at 0.71 for x≤0.54 but appears to change quite abruptly to a fairly constant value of 0.82 for x≥0.58.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357527
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of the conduction-band discontinuity in pseudomorphic InxGa1−xAs/In0.52Al0.48As heterostructures (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 733-735 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Compositional dependence of the conduction-band discontinuity ΔEc in InxGa1−xAs/In0.52Al0.48As pseudomorphic heterostructures has been measured as a function of InAs mole fraction over the range of 0.44≤x≤0.64 using both current-versus-voltage-versus-temperature and capacitance-versus-voltage measurements on semiconductor-insulator-semiconductor structures. The results show a monotonic increase of effective ΔEc with InAs mole fraction x according to ΔEc≈0.384+0.254x for x≤0.54 and an abrupt shift to ΔEc≈0.344+0.487x for x≥0.58. The effects of the conduction-band nonparabolicity and the lattice strain on the Fermi potential have been taken into account in deducing ΔEc from the measured barrier height across the InxGa1−xAs/In0.52Al0.48As heterojunction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.106552
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    High-resolution x-ray characterization of low-temperature GaAs/As superlattice grown by molecular-beam epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3626-3628 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution x-ray analysis of Si delta-doped GaAs grown by molecular-beam epitaxy at a low substrate temperature (230 °C) is presented. Superlattice satellite peaks in the rocking curve are observed for the sample annealed at 700 °C for 10 min. The peak intensity increases with increasing postgrowth annealing temperature and reaches the maximum value for the 900 °C annealed sample. The evolution of the x-ray rocking curves can be explained consistently by the formation of a GaAs/As superlattice during the annealing period based on the transmission electron microscope observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111225
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Two-dimensional arsenic precipitation by In delta doping during low temperature molecular beam epitaxy growth of GaAs or AlGaAs (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2517-2519 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low temperature (LT) GaAs delta doped with In and Al have been grown by molecular beam epitaxy and annealed at 600–900 °C for 10 min. As precipitates have been observed to form preferentially on In doping planes while depleting on the Al planes. Similar As precipitates in In-doped LT-Al0.25Ga0.75As are 50% more efficient than that of GaAs. The accumulation or depletion of As precipitates in two-dimensional planes in LT materials using isoelectronic impurities show that the phenomena is not directly related to the electronic properties of dopant impurities and therefore has many device applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111559
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  • 6
    Electronic Resource
    Electronic Resource
    Strong accumulation of As precipitates in low temperature InGaAs quantum wells grown by molecular beam epitaxy (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1546-1548 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low temperature InGaAs strained quantum wells have been grown by molecular beam epitaxy and annealed at 600–900 °C for 10 min. For an optimized annealing condition, arsenic precipitates can be successfully confined in the InGaAs wells and completely depleted in the GaAs barriers. The strong accumulation of As precipitates shows that the phenomena are not due to the strain effect but may be explained by the difference of interfacial energy between precipitate and matrix. The ability to control the As precipitates into two-dimensional quantum wells in LT materials has unique applications in a wide variety of devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111861
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  • 7
    Electronic Resource
    Electronic Resource
    Nonalloyed InGaAs/GaAs ohmic contacts for self-aligned ion implanted GaAs heterostructure field effect transistors (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2455-2457 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonalloyed indium gallium arsenide (InGaAs) ohmic contacts were investigated and successfully applied to both n- and p-type self-aligned ion implanted heterostructure field effect transistors (HFETs). The key factor was to preserve the doping concentration and structure integrity of the InGaAs layer during implant activation. Specific contact resistances in the range of 5×10−6–2×10−5 Ω cm for n and p HFETs were realized with this structure and process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108150
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of Gibbs free energies of formation for the silicates MnSiO3, Mn2SiO4 and Mn7SiO12 in the temperature range 1000–1350 K by solid state emf measurements (1994)
    Springer
    Physics and chemistry of minerals 21 (1994), S. 228-233 
    Details
    ISSN: 1432-2021
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Abstract Standard Gibbs free energies of formation (A f G0) for the minerals rhodonite (MnSiO3), tephroite (Mn2SiO4) and braunite (Mn7SiO12) have been determined by measuring the oxygen fugacities of the following redox equilibria: 3Mn2SiO4(s)+1/2O2(g)⇌3MnSiO3(s)+Mn3O4(s) MnSi03(s)+2Mn3O4(s)+1/22O2(g)⇌Mn7SiO12(s) and 7MnSiO3(s)+3/2O2(g⇌Mn7SiO12)(s)+6SiO2(s) The measurements were performed by means of the solid-state emf technique involving calcia-stabilized zirconia as electrolyte material. The temperature range covered was 1000–1350 K. The results obtained were used to construct a diagram at 1200 K with the axes lgf(O2)-molar ratio Si/(Si+Mn) to indicate the stability ranges of the manganese silicates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202136
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Magnetic properties and microstructure of lanthanum-doped Mn-Al and Mn-Al-C permanent magnets (1994)
    Springer
    Journal of materials science 29 (1994), S. 4819-4823 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract (Mn0.54Al0.46) 100−x La x and (Mn0.535Al0.448C0.017) 100−x La x alloys, with x up to 0.9, were synthesized and examined by powder X-ray diffraction and magnetic measurements. Lattice parameters, Curie temperature, T c, coercivity, iH c, and saturation magnetization, M s, were determined. Phase analysis revealed that Al8LaMn4 precipitates were produced due to the lanthanum addition. A slight increase in the iH c was observed for x ≤ 0.3 in the cast MnAlLa alloys. No significant changes in lattice parameters and T c were observed for these lanthanum-doped alloys. For sintered isotropic magnets, which were prepared by conventional powder metallurgy processes, the iH c was enhanced on doping with lanthanum. The (BH)max values were also increased. The increment of (BH)max was about 16% for x = 0.3. Higher lanthanum intensity at grain boundaries was observed on examination of the energy-dispersive X-ray spectra (EDX). The reasons for the increase in iH c may be due to the fine precipitates of lanthanum in the grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356528
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