Papers by Author: Ulrike Grossner

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Authors: G. Pasold, F. Albrecht, Joachim Grillenberger, Ulrike Grossner, C. Hülsen, R. Sielemann, W. Witthuhn
Authors: Mads Mikelsen, Ulrike Grossner, Jan H. Bleka, Edouard V. Monakhov, Bengt Gunnar Svensson, Rositza Yakimova, Anne Henry, Erik Janzén, Alexander A. Lebedev
Authors: Pawel A. Sobas, Ulrike Grossner, Bengt Gunnar Svensson
Abstract: Using impedance spectroscopy (IS) for the characterization of SiO2/4H-SiC (MOS) structures, insight on the capacitive and resistive contributions in different physical regions of the MOS structures is obtained. Changing the DC bias conditions, semiconductor, interface as well as oxide traps can be detected. The MOS capacitance, as extracted from IS data, is different from the one obtained using capacitance voltage (CV) measurements, due to the possibility of distinguishing different charge transfer processes using IS. For instance, in the investigated capacitors, a clear contribution is revealed from ionic conduction processes at bias voltages close to zero.
Authors: Marc Avice, Ulrike Grossner, Edouard V. Monakhov, Joachim Grillenberger, Ola Nilsen, Helmer Fjellvåg, Bengt Gunnar Svensson
Abstract: In this study, electrical properties of Al2O3 deposited by Atomic Layer Deposition (ALCVD) on n-type 4H-SiC were investigated. Metal-Oxide-Semiconductor (MOS) capacitors were characterized by various electrical techniques such as Capacitance-Voltage (CV), Current- Voltage (IV) and Deep Level Transient Spectroscopy (DLTS) measurements. Two different oxidants, H2O and O3, have been used for the oxide deposition. After deposition, the flat-band voltage shift is much less using O3 than H2O (~ 7V versus ~ 20V). Annealing treatment has been carried out at different temperatures in Ar atmosphere up to 700°C. Whereas the flat-band voltage shift can be reduced by annealing, the leakage current remains rather high.
Authors: Jody Fronheiser, Aveek Chatterjee, Ulrike Grossner, Kevin Matocha, Vinayak Tilak, Liang Chun Yu
Abstract: The gate oxide reliability and channel mobility of carbon face (000-1) 4H Silicon Carbide (SiC) MOSFETs are investigated. Several gate oxidation processes including dry oxygen, pyrogenic steam, and nitrided oxides were investigated utilizing MOS capacitors for time dependent dielectric breakdown (TDDB), dielectric field strength, and MOSFETs for inversion layer mobility measurements. The results show the C-face can achieve reliability similar to the Si-face, however this is highly dependent on the gate oxide process. The reliability is inversely related to the field effect mobility where other research groups report that pyrogenic steam yields the highest electron mobility while this work shows it has weakest oxide in terms of dielectric strength and shortest time to failure.
Authors: Morten Kildemo, Ulrike Grossner, M. Juel, B. Samuelsen, Bengt Gunnar Svensson, S. Raaen
Authors: Ulrike Grossner, J. Furthmüller, Friedhelm Bechstedt
Authors: Marc Avice, Ulrike Grossner, Ola Nilsen, Jens S. Christensen, Helmer Fjellvåg, Bengt Gunnar Svensson
Abstract: Al2O3 has been grown by Atomic Layer Chemical Vapour Deposition (ALCVD) on ntype 4H-SiC using O3 as an oxidant. After post-deposition, annealing at high temperature (1000°C) in Argon atmosphere for different time periods (1h, 2h, 3h) was performed. Bulk and interface properties of the as-grown as well as the annealed films were studied by electrical measurements (CV, IV, DLTS) and Secondary Ion Mass Spectrometry (SIMS) measurements. The electrical measurements show a decreasing shift of the flatband voltage indicating a diminution of the negative oxide charges with increasing annealing time. After annealing at 1000°C for 3h, the flatband voltage shift has decreased to 6V. The SIMS measurements indicate a double interface with a SiOx (x ≤ 2) interlayer in the as-grown samples while only one interface is observed after annealing, leading to improved electrical behavior of the Metal-Oxide-Semiconductor devices.
Authors: Ulrike Grossner, Marc Avice, Spyros Diplas, Annett Thøgersen, Jens S. Christensen, Bengt Gunnar Svensson, Ola Nilsen, Helmer Fjellvåg, John F. Watts
Authors: Ioana Pintilie, K. Irmscher, Ulrike Grossner, Bengt Gunnar Svensson, Bernd Thomas
Abstract: Nitrogen doped 4H-SiC epitaxial layers grown by hot-wall chemical vapor deposition were investigated by Deep Level Transient Spectroscopy after irradiation with 6 MeV electrons at room temperature. This study is focusing on the influence of nitrogen doping and C/Si ratio on the behaviour of the Z1,2 and EH6,7 levels which occur in already as-grown material but are substantially enhanced by electron and ion irradiation. It was found that both the Z1,2 and EH6,7 concentrations increase with both the nitrogen doping and the C/Si ratio. However, while the Z1,2 concentration increases during post-irradiation thermal treatment the opposite holds for the EH6,7 level especially in silicon rich samples. On the basis of these results, the influence of carbon and nitrogen on the formation of the Z1,2 complex is reconfirmed and a possible identity of the EH6,7 defect is discussed.
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