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  • 1
    Electronic Resource
    Electronic Resource
    Lifetime spectroscopy for defect characterization: Systematic analysis of the possibilities and restrictions (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 2059-2070 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Carrier lifetime is very sensitive to electrically active defects. Apart from detecting the presence of recombination active defects, lifetime measurements allow for a direct identification of defects if the temperature and injection dependence of carrier lifetime is analyzed. In the present work, the Shockley–Read–Hall (SRH) equation is analyzed from a theoretical point of view in order to demonstrate the possibilities and basic restrictions of i(underbar)njection- and t(underbar)emperature-d(underbar)ependent l(underbar)ifetime s(underbar)pectroscopy (IDLS and TDLS), respectively. To show the variety of attainable curve shapes and to evaluate their suitability for a spectroscopic determination of defect parameters, the general impact of the defect and material parameters on the injection and temperature dependence of SRH lifetime is investigated systematically. From this the basic requirements for an unambiguous defect characterization are derived. The experimental applicability of lifetime spectroscopy is demonstrated by TDLS and IDLS measurements performed on an intentionally molybdenum contaminated Si sample using the microwave-detected photoconductance decay technique and the quasi-steady-state photoconductance technique, respectively. The energy level of 0.335 eV below the conduction band determined from TDLS corresponds well with deep level transient spectroscopy-values reported in literature and could also be determined from the corresponding IDLS curve though not unambiguously. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1428095
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  • 2
    Electronic Resource
    Electronic Resource
    Field-effect passivation of the SiO2Si interface (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 683-691 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The field-effect passivation of the interface of thermal oxides on silicon is experimentally investigated by depositing corona charges on the oxide of solar cells and of lifetime test structures. The open circuit voltage of solar cells with interdigitated rear contacts can be increased by +12 mV or decreased by −34 mV, respectively, by depositing positive or negative corona charges on top of the front oxide. The resulting effective surface recombination velocity, Seff, is determined on carrier lifetime test structures for different injection levels and charge densities using microwave-detected photoconductance decay and a new expression for the Auger-limited bulk lifetime. Seff can be varied between 24 cm/s and 538 cm/s on a 1 Ω cm p-type wafer with a thermal oxide of 105 nm thickness. The measurements are compared with theoretical predictions of an analytical model for the calculation of the surface recombination. Measured values for the capture cross sections and interface trap densities are used for the calculation. The model predicts an optimum passivation for strong positive compared to strong negative charge densities. This is due to the asymmetry of the capture cross sections for electrons and holes. This prediction is in very good agreement with the measured Seff values. However, the predicted Seff values of well below 1 cm/s for 1 Ω cm p-type silicon cannot be achieved in the experiment. This discrepancy can be explained by an inhomogeneous charge distribution resulting in potential fluctuations and additional loss currents. With a new extended analytical model for the calculation of Seff the measured Seff values can be described quantitatively. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370784
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  • 3
    Electronic Resource
    Electronic Resource
    Minority carrier lifetime degradation in boron-doped Czochralski silicon (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2397-2404 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The minority carrier lifetime in boron-doped oxygen-contaminated Czochralski (Cz) silicon is strongly reduced under illumination or carrier injection. This process can be fully reversed by a 200 °C anneal step. In several recent studies it was shown that boron and oxygen are the major components of the underlying metastable Cz-specific defect. The energy level of the defect in its active state A was determined to be around midgap [Schmidt et al., J. Appl. Phys. 86, 3175 (1999)] while the energy level of the defect in its passive state P is very shallow. The Cz-specific defect in its passive state can be identified with the shallow thermal donor. The kinetics of the excess carrier-induced transformation from state P to state A can be described using recombination-enhanced defect reaction theory. On the basis of these experimental facts different solutions for the reduction or elimination of the metastable defect are suggested. Two promising solutions are discussed in more detail: the use of gallium-doped Cz silicon and the introduction of high-temperature anneals into the process sequence. Gallium-doped Cz silicon shows no degradation and excellent lifetimes over a wide resistivity range, although the concentration of interstitial oxygen is in the same range as in standard Cz silicon. Stable solar cell efficiencies comparable to FZ silicon have been achieved. If standard boron-doped Cz silicon is used, the defect concentration can be reduced permanently by a high-temperature anneal using conventional tube or rapid thermal processing. This leads to an improvement of the carrier lifetime by a factor of 2–3. Nevertheless, it is always necessary to use an optimized set of process parameters because otherwise the lifetime of all oxygen-contaminated materials (including gallium-doped Cz silicon) is severely reduced © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1389076
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  • 4
    Electronic Resource
    Electronic Resource
    A directional bias for studies of laterality
    Amsterdam : Elsevier
    Neuropsychologia 27 (1989), S. 251-257 
    Details
    ISSN: 0028-3932
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Psychology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0028-3932(89)90177-2
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