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  • 1
    Electronic Resource
    Electronic Resource
    Photoluminescence and photoluminescence excitation studies on GaAs/Al0.25Ga0.75As asymmetric coupled double quantum well (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 3475-3478 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) and PL excitation (PLE) experiments on a GaAs/Al0.25Ga0.75As asymmetric coupled double quantum well are reported. In PLE, the seven peaks, four related to the heavy-hole coupled and the rest to the light-hole coupled excitonic states, are observed. The positions of seven peaks observed in PLE are in good agreement with the calculated results of multi-band envelope function approximation using the transfer matrix method. The result of the temperature-dependent PL above 100 K shows that, even though the wavefunctions are localized in different wells separated by 8 monolayer barrier, the heavy-hole coupled excitons in the two lowest levels are in thermal equilibrium. The observed activation energy is equal to the difference between the two levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354524
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A theory of cavity excitation by modulated electron beam in connection with application to a klystron amplifier (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1349-1357 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Based on an equivalent circuit representation of a cavity impedance, a theoretical model of the cavity excitation by a modulated electron beam is developed. The beam current modulation is initiated by the first cavity and amplified in drift section between the first and second cavities. Properties of the second cavity excitation by the beam are described in terms of the phase shift Ψ and amplitude φ2 of induced voltage in the cavity. The phase shift Ψ and amplitude φ2 are determined in terms of the frequency difference (η), the cavity Q value, the voltage multiplication factor (χ), and magnitude (φ1) of the first cavity voltage. The voltage multiplication factor is proportional to the beam intensity, Q value, and distance between the first and second cavities. On the other hand, it is inversely proportional to frequency and capacitance of the cavity, and beam electron velocity. Because the induced voltage in the second cavity is in phase with the first cavity voltage at upshifted cavity frequency, amplitude of the current modulation at the upshifted frequency is larger than that at the downshifted cavity frequency. Experimental study is carried out by making use of a klystron amplifier operable from 4.4 to 5 GHz. Experimental data from the klystron agree remarkably well with amplifier performance profiles predicted by the theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860924
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  • 3
    Electronic Resource
    Electronic Resource
    Linear analysis of backward wave oscillations in azimuthally varying transverse electric (TE) modes (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1639-1646 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A linear analysis for a gyrotron backward wave oscillator operating at a general transverse electric (TEln) mode of a cylindrical waveguide (slotted or uniform cross section) has been developed using a Maxwell–Vlasov equation under the tenuous beam approximation. The equation is solved by Laplace transformation to allow easy insertion of the boundary values. The start-oscillations conditions are determined from an interference of the waveguide and beam modes with appropriate amplitudes and phases. The theory is used to determine the design parameters for stable operation of a second cyclotron harmonic gyropeniotron amplifier at 35 GHz in the π mode of a six vane magnetron-type circuit with a 70 kV, 3 A beam.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860960
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  • 4
    Electronic Resource
    Electronic Resource
    Time-resolved study of yellow and blue luminescence in Si- and Mg-doped GaN (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 840-842 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time-resolved photoluminescence has been employed to study the donor-acceptor pair recombination kinetics of the yellow (∼2.3 eV) and blue (∼2.8 eV) luminescence bands in Si- and Mg-doped GaN layers, respectively. As the Si doping concentration in Si-doped GaN increases, the lifetime τ1/e of the yellow luminescence decreases, indicating that a shallow Si donor is the origin of the yellow luminescence. The blue luminescence is most likely due to a shallow Mg acceptor and a deep donor composed of a Mg acceptor-nitrogen vacancy complex, as seen by the independence of τ1/e on the Mg concentration measured by secondary ion mass spectroscopy in the range (2.5–6.0)×1019 cm−3. As the temperature is increased from 10 to 300 K, the lifetimes for the yellow and blue luminescence remain nearly constant, indicating that the distribution of electrons and holes bound to donors and acceptors does not change much with increasing temperature. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125602
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  • 5
    Electronic Resource
    Electronic Resource
    Lasing from InGaAs/GaAs quantum dots with extended wavelength and well-defined harmonic-oscillator energy levels (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3351-3353 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented on the lasing transitions from InGaAs/GaAs quantum dots that exhibit four well-resolved energy transitions, with the electronic state density of a two-dimensional harmonic oscillator. Lasing has been obtained on the second and third transitions, depending on the cavity (gain) length, with the longest lasing wavelength measured to be 1.19 μm. The temperature dependence of threshold is studied and regions of nearly temperature-independent threshold are found. Interesting aspects of the unique electronic state density for lasers are discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122766
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  • 6
    Electronic Resource
    Electronic Resource
    Study of surface-emitted stimulated emission in GaN (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 729-731 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of a study of spatially resolved surface-emitted stimulated emission in GaN epilayer samples under conditions of strong optical pumping. We observe that even at excitation powers near the damage threshold, no surface-emitted stimulated emission occurs from samples with a high quality GaN epilayer. In parts of the samples with inferior surface quality, we show that stimulated emission comes from cracks, burned spots, and other imperfections, and is due to the scattering of a photon flux propagating parallel to the surface. Our results suggest that these defects are effective scattering centers and can severely affect the accuracy of optical gain measurements. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119627
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  • 7
    Electronic Resource
    Electronic Resource
    1.3 μm room-temperature GaAs-based quantum-dot laser (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2564-2566 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature lasing at the wavelength of 1.31 μm is achieved from the ground state of an InGaAs/GaAs quantum-dot ensemble. At 79 K, a very low threshold current density of 11.5 A/cm2 is obtained at a wavelength of 1.23 μm. The room-temperature lasing at 1.31 μm is obtained with a threshold current density of 270 A/cm2 using high-reflectivity facet coatings. The temperature-dependent threshold with and without high-reflectivity end mirrors is studied, and ground-state lasing is obtained up to the highest temperature investigated of 324 K. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122534
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of CeO2 interlayer deposition temperature on growth behavior of Bi4Ti3O12/CeO2/MgO heterostructures (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 1077-1079 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: CeO2 interlayers were used to control growth behavior of Bi4Ti3O12 thin films on MgO(001) substrates. The CeO2 layer grown at 740 °C had a preferential orientation with its c-axis normal to the film surface, so it could be used to grow an epitaxial Bi4Ti3O12(001)/CeO2(001)/MgO(001) heterostructure. On the other hand, the CeO2 layer grown at 650 °C showed a mixed texture of (001) and (111), and this interlayer enabled us to get a preferentially oriented Bi4Ti3O12(117)/CeO2(111)MgO(001) multilayer structure. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117063
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  • 9
    Electronic Resource
    Electronic Resource
    Absolute magnetic penetration depth of thin-film niobium measured by fluxoid quantization (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2122-2124 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The absolute magnetic penetration depth of a superconducting niobium film is measured using fluxoid quantization. Laser pulses drive part of a thin, planar niobium loop normal, changing its quantum fluxoid state. We determine the total inductance of the loop by measuring the coupling of the fluxoid to a superconducting quantum interference device at various loop temperatures. We fit the temperature dependence of the inductance data to the Bardeen–Cooper–Schrieffer (BCS) theory to determine the magnetic and kinetic inductances. The kinetic inductance is directly related to the penetration depth through the geometry of the loop, and the measured penetration depth agrees well with the BCS theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109446
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  • 10
    Electronic Resource
    Electronic Resource
    Fully sealed, high-brightness carbon-nanotube field-emission display (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3129-3131 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fully sealed field-emission display 4.5 in. in size has been fabricated using single-wall carbon nanotube (CNT)-organic binders. The fabricated displays were fully scalable at low temperature, below 415 °C, and CNTs were vertically aligned using paste squeeze and surface rubbing techniques. The turn-on fields of 1 V/μm and field emission current of 1.5 mA at 3 V/μm (J=90 μA/cm2) were observed. Brightness of 1800 cd/m2 at 3.7 V/μm was observed on the entire area of a 4.5 in. panel from the green phosphor-indium–tin–oxide glass. The fluctuation of the current was found to be about 7% over a 4.5 in. cathode area. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.125253
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