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  • 1
    Electronic Resource
    Electronic Resource
    Hybrid pole pieces for permanent magnets : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5199-5201 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Highly uniform magnetic fields for nuclear-magnetic-resonance imaging require accurate design of the pole pieces of a permanent magnet structure. We present a mathematical theory of pole pieces viewed as filters that eliminate selected harmonics of an expansion of the field distortion. Previous work has discussed two types of filters: active pole pieces and passive pole pieces. These are reviewed and a third type of filter, the hybrid pole piece, is introduced. The hybrid pole piece provides distinct advantages by combining features of both active and passive pole pieces. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361339
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  • 2
    Electronic Resource
    Electronic Resource
    Maximally efficient permanent magnet structures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1157-1163 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A general theory is developed for determining the most efficient magnetic structure that generates a specified magnetic field. The structure is assumed to be composed of linear, isotropic magnetized material, occupying a given geometrical region. The efficiency is quantified by a figure of merit defined as the external field energy produced by the magnet divided by the maximum amount of energy that can be stored by the magnetized material. A set of equations is derived that determines the distribution of remanence needed to maximize this figure of merit, and several theorems concerning maximally efficient structures are given. Simple two-dimensional examples are used to illustrate the theory. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360914
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of field orientation on field uniformity in permanent magnet structures : The 6th joint magnetism and magnetic materials (MMM)−intermag conference (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6853-6855 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of magnetic-field orientation are investigated for permanent magnet structures designed for the generation of highly uniform fields. The structures considered are based on closed cavities that produce exactly uniform internal fields. An open structure with an approximately uniform field is obtained by removing part of the wall from such a cavity. This paper explores how the magnetic-field uniformity depends on the field orientation relative to the opening. A yokeless, cylindrical cavity that is opened at both ends is considered in detail with the field oriented both perpendicular to and parallel to the cylinder's axis. The field uniformity is shown to be substantially better for the perpendicular orientation. The leakage field outside the magnet is also contrasted for the two cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358092
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  • 4
    Electronic Resource
    Electronic Resource
    Numerical and experimental studies of the intrinsic performance of AlInAs/GaInAs heterojunction bipolar transistors (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4426-4430 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper discusses selected design issues important to the operation of high-speed AlInAs/GaInAs heterojunction bipolar transistors (HBTs). Simulation results reveal that velocity overshoot is an important effect in AlInAs/GaInAs HBTs. It is found to first order that the electron average speed through the base and base/collector depletion region is near 5×107 cm/s. Introduction of a built-in electric field in the base region improves the ft. However, the resultant improvement of the cutoff frequency in the AlInAs/GaInAs HBT is not as significant as in the AlGaAs/GaAs HBT because of the already larger electron velocity in the GaInAs base. Compositional grading in the emitter is not suggested in AlInAs/GaInAs HBTs because it degrades the dc and ac characteristics. The effects of a base setback layer at the emitter/base junction on dc current gain and cutoff frequency have also been studied. It is found that both the doping density and the thickness of the setback layer affect the cutoff frequency, and that the setback layer always degrades the intrinsic performance. The intrinsic setback layer has the lowest cutoff frequency while p-doped setback layer has the highest one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348369
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  • 5
    Electronic Resource
    Electronic Resource
    Optical properties of InAlGaAs quantum wells: Influence of segregation and band bowing (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 2584-2589 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Knowledge of the quaternary InAlGaAs material system is very limited for the composition range relevant for growth on GaAs substrates. We report on the characterization and modeling of InAlGaAs quantum wells with AlGaAs barriers, grown pseudomorphically on a GaAs substrate with molecular beam epitaxy. The quantum wells are characterized with photoluminescence, and the measured transition energies are modeled taking into account the influence of In segregation on the shape of the well potential. From the modeling we deduce a relation for the low temperature band gap of unstrained Inx(AlyGa1−y)1−xAs, for 0≤x,y≤0.20. The measured linewidths of the luminescence peaks are in agreement with the broadening expected from random alloy fluctuations and well width fluctuations with an effective interface roughness of 1.1 ML. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371096
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  • 6
    Electronic Resource
    Electronic Resource
    Ultranarrow polaritons in a semiconductor microcavity (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3262-3264 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have achieved a record high ratio (19) of the Rabi splitting (3.6 meV) to the polariton linewidth (190 μeV), in a semiconductor λ microcavity with a single 25 nm GaAs quantum well at the antinode. The narrow polariton lines are obtained with a special cavity design which reduces the exciton broadening due to scattering with free charges and has a very low spatial gradient of the cavity resonance energy. Since the static quantum-well disorder is very small, the polariton broadening is dominantly homogeneous. Still, the measured linewidths close to zero detuning cannot be correctly predicted using the linewidth averaging model. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126601
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  • 7
    Electronic Resource
    Electronic Resource
    Excimer laser-assisted metalorganic vapor phase epitaxy of CdTe on GaAs (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1434-1436 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have successfully grown CdTe (111) on GaAs (100) at 165 °C using a 248 nm excimer laser to photodissociate dimethylcadmium and diethyltellurium in the gas phase. Good crystalline quality of the layers is confirmed by x-ray diffractometry. Growth rates up to 2 μm/h have been recorded in real time using time-resolved reflectivity. Auger analysis reveals that the films are stoichiometric throughout the thickness of the layer, and that carbon and oxygen contaminants are below the level of detectability. We have used laser-induced fluorescence spectroscopy to examine the photodissociation mechanism of diethyltellurium and have observed a linear dependence of Te atom production on excimer laser power.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99137
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  • 8
    Electronic Resource
    Electronic Resource
    Conductance quantization above 30 K in GaAlAs shallow-etched quantum point contacts smoothly joined to the background 2DEG (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 607-609 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical characteristics of shallow etched GaAs/GaAlAs quantum point contacts (QPCs) of various shapes have been studied as a function of temperature above 0.3 K. Quantized conductance was observed up to 36 K, and from the temperature dependence of the conductance staircase we find energy separations between the lowest one-dimensional subbands up to 20 meV. This value exceeds the highest values so far reported for laterel QPC constrictions in GaAs/GaAlAs heterostructures. In addition, very well behaved quantized conductance plateaus were observed at the lowest temperatures. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366724
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  • 9
    Electronic Resource
    Electronic Resource
    Erratum: "Maximally efficient permanent magnet structures'' [J. Appl. Phys. 79, 1157 (1996)] (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1941-1941 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363831
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  • 10
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    Long carrier lifetimes in large-grain polycrystalline CdTe without CdCl2 (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-06-28
    Description: For decades, polycrystalline CdTe thin films for solar applications have been restricted to grain sizes of microns or less whereas other semiconductors such as silicon and perovskites have produced devices with grains ranging from less than a micron to more than 1 mm. Because the lifetimes in as-deposited polycrystalline CdTe films are typically limited to less than a few hundred picoseconds, a CdCl 2 treatment is generally used to improve the lifetime; but this treatment may limit the achievable hole density by compensation. Here, we establish methods to produce CdTe films with grain sizes ranging from hundreds of nanometers to several hundred microns by close-spaced sublimation at industrial manufacturing growth rates. Two-photon excitation photoluminescence spectroscopy shows a positive correlation of lifetime with grain size. Large-grain, as-deposited CdTe exhibits lifetimes exceeding 10 ns without Cl, S, O, or Cu. This uncompensated material allows dopants such as P to achieve a hole density of 10 16  cm −3 , which is an order of magnitude higher than standard CdCl 2 -treated devices, without compromising the lifetime.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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