Papers by Author: Peter Werner

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Authors: Reinhard Kögler, Xin Ou, Nadine Geyer, Pratyush Das Kanungo, Daniel Schwen, Peter Werner, Wolfgang Skorupa
Abstract: Vertical p-type Si nanowires (NWs) "in-situ" doped during growth or "ex-situ" by B ion implantation are investigated regarding their acceptor activation. Due to the much higher surface to volume ratio of the NW in comparison to bulk material the surface effect plays an important role in determining the doping behaviour. Dopant segregation and fixed positive charges at the Si/SiO2 interface result in an acceptor deactivation. The B concentration introduced into the NW has to balance the deactivation effects in order to reach the intended electrical parameters. Scanning spreading resistance microscopy is used for the electrical characterization of the NWs. This analysis method provides images of the local resistivity of NW cross sections. Resistivity data are converted into acceptor concentration values by calibration. The study demonstrates that scanning spreading resistance microscopy is a suitable analysis method capable to spatially and electrically resolve Si NWs in the nanometer-scale. The NW resistivity is found to be size dependent and shows a significant increase as the NW is below 25 nm in diameter. The obtained data can be explained by a core-shell model with a highly conductive NW core and low conductive shell.
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Authors: Alexander A. Tonkikh, Victor Tapio Rangel-Kuoppa, Nikolay D. Zakharov, Wolfgang Jantsch, Peter Werner
Abstract: We report on a specific defect, which may form during the growth of Stranski-Krastanov surfactant-mediated Ge/Si (100) islands. Transmission electron microscopy reveals that these loop-like defects are local and could be represented by a missing plane of Ge atoms inside some of Ge islands. This specific defect may generate an electrically active trap within the Si band gap at about 0.3 eV above the Si valence band edge. Deep level transient spectroscopy reveals that at least 1 % of Ge islands may include such defects.
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