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  • 11
    Electronic Resource
    Electronic Resource
    Reflection high-energy electron diffraction studies of the growth of strained InxGa1−xAs on GaAs substrate by migration-enhanced epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 692-694 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflection high-energy electron diffraction oscillations have been studied during the growth of strained InxGa1−xAs on GaAs by molecular beam epitaxy and migration-enhanced epitaxy. The oscillations decay rapidly for x(approximately-greater-than)0.2 during molecular beam epitaxy, while they persist for a long while during migration-enhanced epitaxy. We believe that the altered surface reconstruction pattern in the latter case changes the growth mode from three-dimensional to a near perfect two-dimensional mode for high strain values. Using migration-enhanced epitaxy, we demonstrate improved channel mobility and performance of GaAs-based modulation-doped field-effect transistors and narrower linewidths in the low-temperature excitonic photoluminescence of In0.1Ga0.9As/Al0.3Ga0.7As quantum wells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103594
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  • 12
    Electronic Resource
    Electronic Resource
    Carrier recombination rate in GaAs-AlGaAs single quantum well lasers under high levels of excitation (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2083-2085 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The carrier recombination rate in GaAs-AlGaAs single quantum well layers is investigated using a small-signal technique for carrier densities from 1017 to 1019/cm3. For carrier densities up to mid 1018/cm3, the inverse of the differential carrier lifetime, 1/τd, increases linearly with the carrier density. The differential rate, however, saturates at higher carrier densities and remains nearly constant for carrier densities higher than 1019/cm3. The deviation from the bulk recombination behavior is due to a portion of the injected carriers populating the semicontinuum states where the rate for the radiative transition is much smaller. The experimental data indicate that the runaway increase of threshold current with decreasing cavity length commonly observed in the short-cavity lasers is mainly due to the loss of carrier confinement at high carrier densities rather than due to fast carrier-depleting processes, such as Auger recombination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102979
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  • 13
    Electronic Resource
    Electronic Resource
    Neutron penumbral imaging at Gekko XII (abstract) : Eighth topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3230-3230 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 14 MeV DT neutrons emitted from a laser-imploded target have been imaged by using a penumbral aperture camera. This system consists of a 6-cm-thick tungsten toroidal aperture, an array of plastic scintillators, an optical fiber coupled two-stage image intensifier, and a cooled CCD camera. A burn region has been observed with a spatial resolution of ∼35 μm at a neutron yield of 5×1011. The spatial resolution was determined by a pixel resolution, the accuracy of the aperture fabrication, the alignment accuracy of the aperture, the signal-to-noise ratio of an encoded image, and the statistical fluctuation in detecting neutrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141645
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  • 14
    Electronic Resource
    Electronic Resource
    The velocity-dissipation probability density function model for turbulent flows (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1437-1449 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In probability density function (pdf) methods, statistics of inhomogeneous turbulent flow fields are calculated by solving a modeled transport equation for a one-point joint probability density function. The method based on the joint pdf of velocity and fluid compositions is particularly successful since the most important processes—convection and reaction—do not have to be modeled. However, this joint pdf contains no length-scale or time-scale information that can be used in the modeling of other processes. This deficiency can be remedied by considering the joint pdf of velocity, dissipation, and composition. In this paper, by reference to the known properties of homogeneous turbulence, a modeled equation for the joint pdf of velocity and dissipation is developed. This is achieved by constructing stochastic models for the velocity and dissipation following a fluid particle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857592
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  • 15
    Electronic Resource
    Electronic Resource
    X-ray and particle diagnostics of a high-density plasma by laser implosion (invited) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 3235-3240 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A series of laser fusion implosion experiments of plastic hollow shell targets was performed by using the Gekko XII glass laser in order to achieve the required fuel areal density for ignition. Introducing random phase plates to improve illumination uniformity, high-density compression of more than 600 times deuterium liquid density has been achieved. The implosion dynamics and symmetry were observed with a spatially resolved x-ray streak camera and an x-ray multiframing camera. The three-dimensional emission profile of the laser-heated plasma was reconstructed from the x-ray images by use of computed tomography and was compared with the laser illumination profiles. The areal density of the imploded core was measured by the neutron activation of a silicon tracer, the secondary reaction method, and the knock-on proton method. Although the measured density and areal density were consistent with those from 1-D hydrodynamic simulation, experimental neutron yields were significantly lower than those predicted by the simulation for convergence ratios larger than 20. This suggests that better implosion uniformity is required to create a hot spark.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141654
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  • 16
    Electronic Resource
    Electronic Resource
    Bioactive Sesquiterpene Polyol Esters from Euonymus bungeanus (1990)
    s.l. : American Chemical Society
    Journal of natural products 53 (1990), S. 603-608 
    Details
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/np50069a010
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  • 17
    Electronic Resource
    Electronic Resource
    Transport properties of InAsxSb1−x (0≤x≤0.55) on InP grown by molecular-beam epitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6819-6822 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular-beam epitaxy has been successfully used to grow InAsxSb1−x on InP substrates with good electrical characteristics. The samples are all n type with electron concentrations varying in the range (3–9)×1015 cm−3. The mobilities are high (70 000 and 110 000 cm2/V s at 300 and 77 K, respectively) in InSb and the alloys. More importantly, the mobilities remain high at the low temperatures in the alloys also, without any type conversion. The mobility data have been analyzed taking into account the appropriate scattering mechanisms. The alloy scattering potential in InAs0.24 Sb0.76 is estimated to be 0.3 V.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345071
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  • 18
    Electronic Resource
    Electronic Resource
    Effect of coherent strain on hydrogenic acceptor levels in InyGa1−yAs/AlxGa1−xAs quantum well structures (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 180-182 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The biaxial strain produced in lattice-mismatched epitaxy can have a substantial effect on the valence band structure. Theoretical results are presented for a hydrogenic acceptor in a quantum well under tensile and compressive strain. The acceptor level energy is a strong function of strain and could be used as a signature for the effect of strain on the valence band structure. Experimental studies are carried out on compressively strained InyGa1−yAs/ AlxGa1−xAs quantum well structures and the acceptor level energy is determined by photoluminescence measurements. Good agreement is found with the experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103977
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  • 19
    Electronic Resource
    Electronic Resource
    GaAs-on-Si: Improved growth conditions, properties of undoped GaAs, high mobility, and fabrication of high-performance AlGaAs/GaAs selectively doped heterostructure transistors and ring oscillators (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 2343-2353 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Improved growth conditions by molecular-beam epitaxy (MBE) and fabrication of state-of-the-art AlGaAs/GaAs selectively doped heterostructure transistors (SDHTs) and ring oscillators on Si substrates are reported. In MBE growth, use of minimum As4:Ga flux ratio during initial nucleation combined with in situ thermal cycles gave a marked improvement in material quality. With this method, FWHM of x-ray rocking curves was measured as low as 135 arcsec for a 3.5-μm-thick GaAs layer on Si. Although 3-μm-thick undoped GaAs buffer layers on p-type Si substrates were fully depleted under a Schottky contact, a parallel n-type conduction path confined in a thin region (〈0.1 μm) near the GaAs/Si interface was sometimes observed whose sheet density (1012–1013 cm−2) and mobility (600–900 cm2 V−1 s−1) were independent of temperature between 300 and 77 K. This parallel conduction was successfully prevented by doping 0.1 μm GaAs with 5–10×1016 cm−3 Be atoms near the interface. In AlGaAs/GaAs selectively doped heterostructures, for a sheet density of 1012 cm−2, a mobility as high as 53 500 cm2 V−1 s−1 at 77 K was obtained, as against a mobility of ∼70 000 cm2 V−1 s−1 for a similar structure on GaAs substrates. For 1-μm-gate-length SDHTs, maximum transconductances of 220 and 365 mS/mm were measured at 300 and 77 K, respectively. A minimum propagation delay time τd of 28 ps/stage was measured at 300 K for ring oscillators at 1.1 mW/stage power dissipation. τd decreased to 17.6 ps/stage at 77 K. From microwave S-parameter measurements at 300 K, current gain and power gain cutoff frequencies of 15 and 22 GHz, respectively, were measured. These results are comparable to that of SDHT technology on GaAs substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345529
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  • 20
    Electronic Resource
    Electronic Resource
    Hydrothermal stability of aluminum borate (1990)
    Springer
    Catalysis letters 6 (1990), S. 225-230 
    Details
    ISSN: 1572-879X
    Keywords: Aluminum borate ; pore size distribution ; surface area ; hydrothermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Aluminum borate with Al to B ratio of 10 was treated with water steam at 750 ° C for up to 48 h. It was found that steam would change the pore size distribution and the surface area of the aluminum borate. It did not possess superior hydrothermal stability under severe conditions. This can be ascribed to high surface instability of transition materials especially for boron compounds. However, even when only a small amount of boron is incorporated into the alumina structure, the surface area of such material can be increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00774724
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