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  • Articles  (33)
  • Articles: DFG German National Licenses  (33)
  • American Institute of Physics (AIP)  (33)
  • International Union of Crystallography
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  • Articles  (33)
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  • 1
    Electronic Resource
    Electronic Resource
    Impurity photovoltaic effect in indium-doped silicon solar cells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4030-4036 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Impurity photovoltaic effect is investigated in two groups of indium-doped single-crystalline silicon solar cells with n-type and p-type dopants in the base layer. The continuity equation for minority carriers is solved numerically using the charge neutrality condition and current–voltage characteristics are found. It is shown that the improvement of short-circuit current due to carrier photogeneration from the deep defect level is negligible for both groups of the cells considered. Short-circuit current increases with increasing the trap concentration and open-circuit voltage abruptly decreases for trap concentrations close to compensation by n-type dopant. However, these dependencies occur due to the increase of lifetime, the decrease of the total equilibrium carrier density, and take place even in the absence of the absorption of subgap photons. It is shown that indium is not the proper impurity for efficiency improvements of silicon solar cells due to the impurity photovoltaic effect. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1354651
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanisms for the anomalous dependence of carrier lifetime on injection level and photoconductance on light intensity (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 332-335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent experiments indicated an anomalous dependence of carrier lifetime on injection level and of photoconductance on carrier photogeneration rate. In this work mechanisms for these phenomena are proposed which are based on the effects of anomalous increase of carrier lifetime and filling of the defect level by minority carriers, respectively. Distinct from previously known mechanisms, which considered two types of deep defects, traps and recombination centers, our mechanism may take place in semiconductors containing only one type of deep defect, which is a recombination center. It was shown that the anomalous injection-level dependence of lifetime occurs only when the semiconductor is exactly compensated by recombination centers. This conclusion differs from that of the previous model, which concluded that carrier trapping is responsible for the earlier phenomenon. It is shown that the injection-level dependence of carrier lifetime can be used as an experimental tool to determine the deep defect concentration. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1330768
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  • 3
    Electronic Resource
    Electronic Resource
    Relaxation of a nonideal magnetohydrodynamic plasma in a cylindrical column (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2525-2530 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The time evolution of a nonideal magnetohydrodynamic (MHD) plasma is investigated. An approach for the reduction of the nonlinear vector MHD equations for a current carrying plasma with a strong longitudinal external magnetic field to a set of scalar partial differential equations is supposed. Analytical time-dependent solutions of the nonlinear resistive and dissipative MHD equations for a cylindrical plasma column are presented. It is shown that the internal magnetic field and the velocity have different damping times and that in the asymptotic limit t→∞ the plasma slowly relaxes toward the static equilibrium state. Analytical reduced MHD solutions describing slowly evolving states in tokamaks are found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870580
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  • 4
    Electronic Resource
    Electronic Resource
    Energy transfer via a thermal capillary (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 4898-4901 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal radiation transfer in a cylindrical hohlraum is discussed. The mass and energy conservation equations for the ablated wall material, derived from the self-similar solution for ablative heat wave [R. Pakula and R. Sigel, Phys. Fluids 28, 232 (1985)], and coupled flux conservation equation, are solved to investigate energy redistribution inside the hohlraum. A similarity solution is obtained for a gold capillary heated by a uniform disc source, with which the re-emission flux from the wall and the energy transfer efficiency through the thermal capillary are calculated for different parametric conditions. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1403695
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  • 5
    Electronic Resource
    Electronic Resource
    Global Alfvén eigenmodes in a stellarator with trapped energetic particles (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2462-2471 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The presence of a super-thermal ion component in tokamak as well as in stellarator plasmas, can give rise to Alfvén-type instabilities. In the present paper an analytical investigation of global Alfvén eigenmodes (GAEs) in a stellarator with planar magnetic axis is performed and analytical expressions for the dominant mode numbers are derived. The effect of trapped highly energetic particles on the GAEs is investigated. The frequencies and corresponding growth rates of the discrete GAE spectrum are found for different distributions of the energetic particles. It is shown that for given background conditions, the slowing-down distributions yield the largest values for the growth rates. The inclusion of the highly energetic particles leads to a change of the conditions for the existence of GAEs and in the dominant mode numbers. A shear dependent threshold for the pressure of the trapped energetic particles has been found, above which GAEs cannot be excited. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873518
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  • 6
    Electronic Resource
    Electronic Resource
    Three-dimensional Fokker–Planck equation for trapped fast ions in a Tokamak with weak toroidal field ripples (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3853-3867 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The five-dimensional (5D) drift kinetic Fokker–Planck equation for fast charged particles confined in a tokamak with a toroidal field (TF) ripple magnitude below the Goldston–White–Boozer stochasticity threshold is averaged over the banana and superbanana timescales. As a result, a three-dimensional (3D) Fokker–Planck equation in the constants of motion (COM) space describing the collisional transport of charged high-energy particles is obtained. Toroidally trapped particles with the toroidal precession being in resonance with the ripple perturbations are shown to yield the main contribution to the ripple induced transport. It is found that the rates of ripple superbanana diffusion and convection in the radial coordinate significantly exceed the corresponding rates of the bananas in the axisymmetric limit. The superbanana diffusion and convection shown to be dominant in the MeV energy range may be responsible for the loss of partially thermalized fusion products observed in the Tokamak fusion test reactor (TFTR) [S. J. Zweben, R. L. Boivin, C.-S. Chang et al., Nucl. Fusion 31, 2219 (1991); H. W. Herrmann, S. J. Zweben, D. S. Darrow et al., ibid. 37, 1437 (1997)]. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873649
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  • 7
    Electronic Resource
    Electronic Resource
    Volmer–Weber and Stranski–Krastanov InAs-(Al,Ga)As quantum dots emitting at 1.3 μm (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6272-6275 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum dots (QDs) formed on GaAs(100) substrates by InAs deposition followed by (Al,Ga)As or (In,Ga,Al)As overgrowth demonstrate a photoluminescence (PL) peak that is redshifted (up to 1.3 μm) compared to PL emission of GaAs-covered QDs. The result is attributed to redistribution of InAs molecules in the system in favor of the QDs, stimulated by Al atoms in the cap layer. The deposition of a 1 nm thick AlAs cover layer on top of the InAs–GaAs QDs results in replacement of InAs molecules of the wetting layer by AlAs molecules, leading to a significant increase in the heights of the InAs QDs, as follows from transmission electron microscopy. This effect is directly confirmed by transmission electron microscopy indicating a transition to a Volmer–Weber-like QD arrangement. We demonstrate an injection laser based on this kind of QDs. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321795
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  • 8
    Electronic Resource
    Electronic Resource
    Study of radiative recombination efficiency in 28–180-Å-wide AlGaAs/GaAs quantum wells grown by molecular beam epitaxy (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 4152-4155 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The paper reports a theoretical and experimental study of the dependence of the radiative recombination efficiency (ηi) on the GaAs quantum well width (Lz) in AlGaAs/GaAs quantum well structures with binary/binary superlattice confinement. Values of ηi(approximately-greater-than)60% at room temperature have been obtained for quantum wells with Lz≥40 A(ring). It is shown that structures with Lz〈40 A(ring) exhibit a sharp decrease in ηi associated with nonradiative recombination of the high energy part of nonequilibrium carriers in the confining layers even in the presence of comparatively high potential barriers for Γ electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357002
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  • 9
    Electronic Resource
    Electronic Resource
    Extremely low threshold current AlGaAs buried-heterostructure quantum well lasers grown by liquid phase epitaxy (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 2873-2875 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented on AlGaAs single quantum well buried-heterostructure lasers grown by two-step liquid phase epitaxy (LPE). The base laser structures were grown by low-temperature LPE in the temperature interval of 600–400 °C. Broad-area threshold current densities of 300 A/cm2 were measured for 1-mm-long lasers. The buried heterostructure was formed in the second LPE process including in situ selective mesa melt etching. Threshold currents of 1.3 mA in a continuous regime were obtained for uncoated lasers having 125-μm-long cavities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103762
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of substrate temperature on the orientation of YBa2Cu3O7 films (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 822-824 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural characteristics of YBa2Cu3O7 (YBCO) thin films were investigated by x-ray diffractometry. Films with good preferred orientation (001) and high Tc0 (86–90 K) can be prepared in situ using the dc magnetron sputtering method. For the films prepared on the ZrO2 (stabilized with Y2O3) substrate at a substrate temperature (Ts) less than 700 °C, there are different orientations and the degree of random orientation will decrease with increasing Ts. YBCO films with (001) can be obtained on ZrO2 with different crystal planes, such as (100), (110), and (111) at suitable temperature (760–850 °C). From the results it could be concluded that the YBCO film growth with c-axis orientation mainly depends on the substrate temperature Ts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104261
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