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  • 1
    Digitale Medien
    Digitale Medien
    Surface diffusion processes in molecular beam epitaxial growth of GaAs and AlAs as studied on GaAs (001)-(111)B facet structures (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 4138-4144 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Mechanisms of molecular beam epitaxy have been investigated for GaAs and AlAs by growing and analyzing the shapes of facet structures consisting of an (001) top surface and two (111)B side surfaces. It is found that all of the Ga flux on the three facet planes is incorporated into the film, but the growth rates on (111)B and (001) depend strongly on the As flux and are mainly determined by the diffusion of Ga ad-atoms between the two planes. In contrast, the diffusion of Al is found to be almost negligible, irrespective of the As flux. By analyzing the shape of the facet, the diffusion length, λ, of Ga on a (001) surface is estimated to be about 1 μm at 580 °C, while that of Al is about 0.02 μm. On (111)B, λ of Ga is found to be several μms. The reflectivity of diffusing Ga atoms is found to be far less than 1 for the (001)-(111)B boundary, and almost unity at facet boundaries where the (111)B side surfaces are bound by the (11¯0) side walls.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.357364
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  • 2
    Digitale Medien
    Digitale Medien
    Study on the preparation of 90-K superconductor LaBa2Cu3Oy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4095-4102 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The high-Tc superconductor LaBa2Cu3Oy has been prepared under various conditions, and characterized by x-ray and neutron powder diffraction techniques, dc and ac magnetic susceptibility measurements, and dc resistivity measurement. It has been found that samples with excellent superconducting characteristics and also with good structural properties are obtained in a reproducible way if the following three procedures are performed: preheat treatment of La2O3 powders, sintering in N2, and low-temperature annealing in dried O2. Long-time annealing in undried O2 was sometimes found to degrade the grain boundaries and to lead to a lower zero-resistance temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.341318
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  • 3
    Digitale Medien
    Digitale Medien
    Evolution of end-of-range damage and transient enhanced diffusion of indium in silicon (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 639-645 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Correlation of evolution of end-of-range (EOR) damage and transient enhanced diffusion (TED) of indium has been studied by secondary ion mass spectrometry and transmission electron microscopy. A physically based model of diffusion and defect growth is applied to the indium diffusion system. Indium implantation with 200 keV, 1×1014/cm2 through a 10 nm screen oxide into 〈100〉 p-type Czochralski silicon wafer was performed. During postimplantation anneal at 750 °C for times ranging from 2 to 120 min, formation of dislocation loops and indium segregation into loops were observed. Simulation results of evolution of EOR defects show that there is a period that {311} defects dissolve and release free interstitials before the Ostwald ripening step of EOR dislocation loops. Our diffusion model that contains the interaction between indium and loops shows the indium pileup to the loops. Indium segregation to loops occurs at a pure growth step of loops and continues during the Ostwald ripening step. Although dislocation loops and indium segregation in the near-surface region are easily dissolved by high temperature annealing, EOR dislocation loops in the bulk region are rigid and well grown. It is considered that indium trapped by loops with a large radius is energetically stable. It is shown that modeling of the evolution of EOR defects is important for understanding indium TED. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1421213
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  • 4
    Digitale Medien
    Digitale Medien
    Effects of end-of-range dislocation loops on transient enhanced diffusion of indium implanted in silicon (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4980-4984 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transient enhanced diffusion of indium implanted in silicon is studied in the presence of the end-of-range (EOR) damage layer. To investigate the effect of EOR defects on the indium diffusion, the samples that were implanted with indium at a high dose (1×1013–5×1014/cm2) sufficient to produce the amorphous layer were prepared. Transmission electron microscopy measurements and Rutherford backscattering spectrometry reveal the amorphization threshold of indium implantation is around 5×1013/cm2 for 200 keV, 115In+ implanted with 100 μA/cm2 beam current density at room temperature. These results are consistent with Monte Carlo simulation of implantation. Monte Carlo simulations indicate the deviation from the plus one model due to the mass effect of indium. After amorphization, following both RTA at 1000 °C and furnace anneal at low temperature (650 and 850 °C) in nitrogen ambient showed the formation of extrinsic EOR dislocation loops below the original amorphous/crystalline interface. During this process, strong segregation of indium toward the EOR dislocation loops is clearly observed. The profile shift of indium at a concentration of 1×1017 atoms/cm3 is not proportional to the implanted dose. Since most interstitials condense into EOR dislocation loops, diffusivity enhancement of indium is not proportional to the implant dose above amorphization threshold. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1314304
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  • 5
    Digitale Medien
    Digitale Medien
    Transport properties of two-dimensional electron gas in AlGaAs/GaAs selectively doped heterojunctions with embedded InAs quantum dots (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3444-3446 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transport properties of two-dimensional electron gas (2DEG) are studied in selectively doped GaAs/n-AlGaAs heterojunctions, in which nanometer-scale InAs dots are embedded in the vicinity of the GaAs channel. When the distance Wd between the InAs dot layer and the channel is reduced from 80 to 15 nm, the mobility μ of electrons at 77 K decreases drastically from 1.1×105 to 1.1 ×103 cm2/V s, while the carrier concentration increases from 1.1×1011 to 5.3×1011 cm−2. Such a reduction of mobility is found only when the average thickness of InAs layer is above the onset level (∼1.5 monolayer) for the dot formation. Origins of these changes in μ and Ns are discussed in connection with dot-induced modulations of the electronic potential V(r) in the channel. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.115274
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  • 6
    Digitale Medien
    Digitale Medien
    A new resistor network for an electrostatic octupole deflector combined with a stigmator (1991)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 240-241 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A new resistor network for an octupole deflector combined with a stigmator is proposed. Improvement on the time constant due to the octupole's stray capacity, which is made by connecting phase-compensative capacitors parallel to the resistors, is also described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1142321
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  • 7
    Digitale Medien
    Digitale Medien
    Correlation length of interface roughness and its enhancement in molecular beam epitaxy grown GaAs/AlAs quantum wells studied by mobility measurement (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1651-1653 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied the correlation length (Λ) of interface roughness in GaAs/AlAs quantum wells (QWs) prepared by molecular beam epitaxy (MBE). It is found that the mobility of two-dimensional electrons in very thin selectively doped GaAs/AlAs QW structures is substantially enhanced when the bottom AlAs barrier layer is prepared by alternate beam MBE and/or by the use of superlattice buffer layer below the QW. By measuring the electron concentration dependence of mobility and comparing with the theory of interface roughness scattering, we have found that Λ of the bottom (GaAs-on-AlAs) interface of the QW gets as large as 200–300 A(ring), when prepared by the modified growth technique, which is about three times as large as that (∼70 A(ring)) by conventional MBE.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.104077
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  • 8
    Digitale Medien
    Digitale Medien
    Interface roughness scattering in GaAs/AlAs quantum wells (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1934-1936 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We study experimentally and theoretically the influence of interface roughness on the mobility of two-dimensional electrons in modulation-doped AlAs/GaAs quantum wells. It is shown that interface roughness scattering is the dominant scattering mechanism in thin quantum wells with a well thickness Lw〈60 A(ring), where electron mobilities are proportional to L6w, reaching 2×103 cm2/V s at Lw∼55 A(ring). From detailed comparison between theory and experiment, it is determined that the "GaAs-on-AlAs'' interface grown by molecular beam epitaxy has a roughness with the height of 3–5 A(ring) and a lateral size of 50–70 A(ring).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.98305
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  • 9
    Digitale Medien
    Digitale Medien
    Resonant tunneling of electrons via 20 nm scale InAs quantum dot and magnetotunneling spectroscopy of its electronic states (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 105-107 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The resonant tunneling of electrons through a 20 nm scale InAs quantum dot bound by a pair of very thin AlAs barriers is studied. A well-resolved composite peak resulting from the ground 1s states was observed at 4.2 K in current–voltage characteristics. By investigating the effects of inplane magnetic fields, the shape of the wave function and the spatial extent of the first two electronic states are clarified. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.119276
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  • 10
    Digitale Medien
    Digitale Medien
    Detection of oxygen incorporated in molecular-beam epitaxy grown GaAs-on-AlAs interfaces and AlAs layers by secondary ion mass spectrometry (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1924-1926 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: By employing a long growth interruption (GI) in molecular beam epitaxy, we have successfully determined the concentration of oxygen incorporated in GaAs/AlAs interfaces and AlAs layers by secondary ion mass spectrometry. The concentration of oxygen atoms incorporated on AlAs surfaces during GI is found to be proportional to the period of GI when the incoming fluxes of residual oxygen-related species reach steady-state values. The net incorporation rate of oxygen on the AlAs surface is found to be constant for a wide range of substrate temperatures from 540 to 620 °C, indicating that the oxygen desorption is negligible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.110650
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