The Experts below are selected from a list of 53778 Experts worldwide ranked by ideXlab platform

D D Awschalom - One of the best experts on this subject based on the ideXlab platform.

  • current induced polarization and the spin hall effect at room temperature
    Physical Review Letters, 2006
    Co-Authors: N P Stern, Sayantani Ghosh, Gang Xiang, N Samarth, D D Awschalom
    Abstract:

    : Electrically induced electron spin polarization is imaged in n-type ZnSe epilayers using Kerr rotation spectroscopy. Despite no evidence for an electrically induced internal magnetic field, current-induced in-plane spin polarization is observed with characteristic spin lifetimes that decrease with Doping Density. The spin Hall effect is also observed, indicated by an electrically induced out-of-plane spin polarization with opposite sign for spins accumulating on opposite edges of the sample. The spin Hall conductivity is estimated as 3+/-1.5 Omega(-1) m(-1)/|e| at 20 K, which is consistent with the extrinsic mechanism. Both the current-induced spin polarization and the spin Hall effect are observed at temperatures from 10 to 295 K.

  • current induced polarization and the spin hall effect at room temperature
    Physical Review Letters, 2006
    Co-Authors: N P Stern, Sayantani Ghosh, Gang Xiang, N Samarth, Meng Zhu, D D Awschalom
    Abstract:

    Electrically induced electron spin polarization is imaged in $n$-type ZnSe epilayers using Kerr rotation spectroscopy. Despite no evidence for an electrically induced internal magnetic field, current-induced in-plane spin polarization is observed with characteristic spin lifetimes that decrease with Doping Density. The spin Hall effect is also observed, indicated by an electrically induced out-of-plane spin polarization with opposite sign for spins accumulating on opposite edges of the sample. The spin Hall conductivity is estimated as $3\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{ }{\ensuremath{\Omega}}^{\ensuremath{-}1}\text{ }{\mathrm{m}}^{\ensuremath{-}1}/|e|$ at 20 K, which is consistent with the extrinsic mechanism. Both the current-induced spin polarization and the spin Hall effect are observed at temperatures from 10 to 295 K.

Wilhelm Warta - One of the best experts on this subject based on the ideXlab platform.

  • comprehensive microscopic analysis of laser induced high Doping regions in silicon
    IEEE Transactions on Electron Devices, 2011
    Co-Authors: Paul Gundel, D Suwito, Ulrich Jager, Friedemann D Heinz, Wilhelm Warta, Martin C Schubert
    Abstract:

    Microscopic laser-doped regions in advanced solar cell concepts are analyzed to determine the Doping Density and to identify the damage caused by the laser process. For these investigations, microphotoluminescence spectroscopy and micro-Raman spectroscopy are utilized to measure Doping Density, internal stress, and carrier lifetime with micrometer resolution. This analysis proves the high applicability of the microspectroscopic techniques for the characterization of laser-doped regions by analyzing the profile of the advanced local Doping process and the laser-induced damage particularly at the edges of the highly doped regions.

  • Micro-spectroscopy on silicon wafers and solar cells
    Nanoscale Research Letters, 2011
    Co-Authors: Paul Gundel, Friedemann D Heinz, Martin C Schubert, Robert Woehl, Jan Benick, Johannes A Giesecke, Dominik Suwito, Wilhelm Warta
    Abstract:

    Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the Doping Density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole Density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the Doping Density and the carrier lifetime in selective emitters, laser fired Doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.

Jean-paul Kleider - One of the best experts on this subject based on the ideXlab platform.

  • Electrical characterization of low temperature plasma epitaxial Si grown on highly doped Si substrates
    EPJ Photovoltaics, 2020
    Co-Authors: Cyril Léon, Marie-estelle Gueunier-farret, Jean-paul Kleider, Sylvain Le Gall, Pere Roca I Cabarrocas
    Abstract:

    Epitaxial silicon layers were grown on highly doped c-Si substrates using the plasma-enhanced chemical vapour deposition process (PECVD) at low temperature (175 °C). The transport and defect-related properties of these epi-Si layers were characterized by current Density-voltage (J–V) and capacitance–voltage (C–V) techniques. The results show that the epi-Si layers exhibit a non-intentional n-type Doping with a low apparent Doping Density of about 2 × 10^15 cm−3. The admittance spectroscopy technique is used to investigate the presence of deep-level defects in the structure. An energy level at 0.2 eV below the conduction band has been found with a Density in the range of 10^15 cm−3 which may explain the observed apparent Doping profile.

  • Modelling on c-Si/a-Si:H wire solar cells: some key parameters to optimize the photovoltaic performance
    EPJ Photovoltaics, 2012
    Co-Authors: Irène Ngo, Marie-estelle Gueunier-farret, José Alvarez, Jean-paul Kleider
    Abstract:

    Solar cells based on silicon nano- or micro-wires have attracted much attention as a promising path for low cost photovoltaic technology. The key point of this structure is the decoupling of the light absorption from the carriers collection. In order to predict and optimize the performance potential of p- (or n-) doped c-Si/ n-(or p-) doped a-Si:H nanowire-based solar cells, we have used the Silvaco-Atlas software to model a single-wire device. In particular, we have noticed a drastic decrease of the open-circuit voltage (Voc) when increasing the Doping Density of the silicon core beyond an optimum value. We present here a detailed study of the parameters that can alter the Voc of c-Si(p)/a-Si:H (n) wires according to the Doping Density in c-Si. A comparison with simulation results obtained on planar c-Si/a-Si:H heterojunctions shows that the drop in Voc, linked to an increase of the dark current in both structures, is more pronounced for radial junctions due to geometric criteria. These numerical modelling results have lead to a better understanding of transport phenomena within the wire.

N P Stern - One of the best experts on this subject based on the ideXlab platform.

  • current induced polarization and the spin hall effect at room temperature
    Physical Review Letters, 2006
    Co-Authors: N P Stern, Sayantani Ghosh, Gang Xiang, N Samarth, D D Awschalom
    Abstract:

    : Electrically induced electron spin polarization is imaged in n-type ZnSe epilayers using Kerr rotation spectroscopy. Despite no evidence for an electrically induced internal magnetic field, current-induced in-plane spin polarization is observed with characteristic spin lifetimes that decrease with Doping Density. The spin Hall effect is also observed, indicated by an electrically induced out-of-plane spin polarization with opposite sign for spins accumulating on opposite edges of the sample. The spin Hall conductivity is estimated as 3+/-1.5 Omega(-1) m(-1)/|e| at 20 K, which is consistent with the extrinsic mechanism. Both the current-induced spin polarization and the spin Hall effect are observed at temperatures from 10 to 295 K.

  • current induced polarization and the spin hall effect at room temperature
    Physical Review Letters, 2006
    Co-Authors: N P Stern, Sayantani Ghosh, Gang Xiang, N Samarth, Meng Zhu, D D Awschalom
    Abstract:

    Electrically induced electron spin polarization is imaged in $n$-type ZnSe epilayers using Kerr rotation spectroscopy. Despite no evidence for an electrically induced internal magnetic field, current-induced in-plane spin polarization is observed with characteristic spin lifetimes that decrease with Doping Density. The spin Hall effect is also observed, indicated by an electrically induced out-of-plane spin polarization with opposite sign for spins accumulating on opposite edges of the sample. The spin Hall conductivity is estimated as $3\ifmmode\pm\else\textpm\fi{}1.5\text{ }\text{ }{\ensuremath{\Omega}}^{\ensuremath{-}1}\text{ }{\mathrm{m}}^{\ensuremath{-}1}/|e|$ at 20 K, which is consistent with the extrinsic mechanism. Both the current-induced spin polarization and the spin Hall effect are observed at temperatures from 10 to 295 K.

Paul Gundel - One of the best experts on this subject based on the ideXlab platform.

  • comprehensive microscopic analysis of laser induced high Doping regions in silicon
    IEEE Transactions on Electron Devices, 2011
    Co-Authors: Paul Gundel, D Suwito, Ulrich Jager, Friedemann D Heinz, Wilhelm Warta, Martin C Schubert
    Abstract:

    Microscopic laser-doped regions in advanced solar cell concepts are analyzed to determine the Doping Density and to identify the damage caused by the laser process. For these investigations, microphotoluminescence spectroscopy and micro-Raman spectroscopy are utilized to measure Doping Density, internal stress, and carrier lifetime with micrometer resolution. This analysis proves the high applicability of the microspectroscopic techniques for the characterization of laser-doped regions by analyzing the profile of the advanced local Doping process and the laser-induced damage particularly at the edges of the highly doped regions.

  • Micro-spectroscopy on silicon wafers and solar cells
    Nanoscale Research Letters, 2011
    Co-Authors: Paul Gundel, Friedemann D Heinz, Martin C Schubert, Robert Woehl, Jan Benick, Johannes A Giesecke, Dominik Suwito, Wilhelm Warta
    Abstract:

    Micro-Raman (μRS) and micro-photoluminescence spectroscopy (μPLS) are demonstrated as valuable characterization techniques for fundamental research on silicon as well as for technological issues in the photovoltaic production. We measure the quantitative carrier recombination lifetime and the Doping Density with submicron resolution by μPLS and μRS. μPLS utilizes the carrier diffusion from a point excitation source and μRS the hole Density-dependent Fano resonances of the first order Raman peak. This is demonstrated on micro defects in multicrystalline silicon. In comparison with the stress measurement by μRS, these measurements reveal the influence of stress on the recombination activity of metal precipitates. This can be attributed to the strong stress dependence of the carrier mobility (piezoresistance) of silicon. With the aim of evaluating technological process steps, Fano resonances in μRS measurements are analyzed for the determination of the Doping Density and the carrier lifetime in selective emitters, laser fired Doping structures, and back surface fields, while μPLS can show the micron-sized damage induced by the respective processes.