Papers by Author: Gerhard Pensl

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Authors: Valeri V. Afanas'ev, Florin Ciobanu, Sima Dimitrijev, Gerhard Pensl, Andre Stesmans
Abstract: Properties of defects encountered at the oxidized surfaces of silicon carbide (SiC) suggest their origin to be different from the dangling-bond-type defects commonly observed in the oxidized silicon. Among different models of these SiC/oxide interface states advanced during the past decade, two have received substantial experimental support. This first one is the “carbon cluster” model, which ascribes the traps with energy levels in the SiC bandgap to inclusions of elemental carbon formed during the SiC surface treatment and subsequent oxidation. The second model invokes intrinsic defects of SiO2 to account for the high density of interface states in the energy range close to the conduction band of SiC. Achievements in reducing the SiC/SiO2 defect density are discussed.
Authors: Gerhard Pensl, Frank Schmid, Sergey A. Reshanov, Heiko B. Weber, M. Bockstedte, Alexander Mattausch, Oleg Pankratov, Takeshi Ohshima, Hisayoshi Itoh
Abstract: Nitrogen (N) donors in SiC are partially deactivated either by Si+-/N+-co-implantation or by irradiation with electrons of 200 keV energy and subsequent annealing at temperatures above 1450°C; simultaneously the compensation is decreased. The free electron concentration and the formation of energetically deep defects in the processed samples are determined by Hall effect and deep level transient spectroscopy. A detailed theoretical treatment based on the density functional theory is conducted; it takes into account the kinetic mechanisms for the formation of N interstitial clusters and (N-vacancy)-complexes. This analysis clearly indicates that the (NC)4-VSi complex, which is thermally stable up to high temperatures and which has no level in the band gap of 4HSiC, is responsible for the N donor deactivation.
Authors: Svetlana Beljakowa, Thomas Frank, Gerhard Pensl, Kun Yuan Gao, Florian Speck, Thomas Seyller
Abstract: An alternative oxidation technique is developed and built up, which provides monatomic oxygen during the whole oxidation process. The set-up consists of a tungsten lamp furnace and a microwave-plasma. A number of different gases can be introduced into the oxidation quartz tube. In addition, an Al2O3-layer is deposited on a part of the oxide layers by atomic layer chemical vapor deposition (ALCVD). First oxidation runs result in encouraging low values of the density of interface states Dit and in the flatband voltage UFB. It turns out that with the present experimental conditions, the comparison of MOS capacitors fabricated with different dielectric layers favors gate dielectrics grown in O2/N2-ambient.
Authors: Ji Sheng Han, K.Y. Cheong, Sima Dimitrijev, Michael Laube, Gerhard Pensl
Authors: Kun Yuan Gao, Thomas Seyller, Konstantin V. Emtsev, Lothar Ley, Florin Ciobanu, Gerhard Pensl
Abstract: Atomic Layer Deposited Al2O3 films on hydrogen-terminated 6H-SiC(0001) were annealed in hydrogen atmosphere and characterized by admittance spectroscopy measurement and photoelectron spectroscopy (PES). The resultant density of interface trap (Dit) from admittance spectroscopy measurement is reduced near mid gap, but increases strongly towards the conduction band edge. Systematic PES measurements show that hydrogen annealing introduces Si4+ as a new component besides Si0 and Si+. Using different electron escape depths for photon electrons, depth profiling of Si in its different oxidation states was performed. The result indicates the formation of a top SiO2 layer and a rougher interfacial layer containing more Si+ and Si4+ which could be responsible for the strong increase of Dit just below the conduction band edge.
Authors: Günter Wagner, W. Leitenberger, K. Irmscher, Frank Schmid, Michael Laube, Gerhard Pensl
Authors: R. Addinall, R.C. Newman, W. Götz, G. Roos, Gerhard Pensl, D.A. Hope
Authors: Atsuo Kawasuso, F. Redmann, Reinhard Krause-Rehberg, Peter Sperr, Thomas Frank, Michael Weidner, Gerhard Pensl, Hisayoshi Itoh
Authors: Michael Krieger, Michael Laube, Michael Weidner, Gerhard Pensl
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