Papers by Author: Anders Hallén

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Authors: Evgenia V. Kalinina, A.S. Zubrilov, V. Solov'ev, N.I. Kuznetsov, Anders Hallén, Andrey O. Konstantinov, S. Karlsson, S.V. Rendakova, Vladimir Dmitriev
Authors: Sethu Saveda Suvanam, M. Usman, K. Gulbinas, V. Grivickas, Anders Hallén
Abstract: This paper aims to establish a new method to characterize the interface between 4H-SiC and passivating dielectric layers. The investigations are made on MOS test structures utilizing Al2O3 and SiO2 dielectrics on 4H-SiC. These devices are then exposed to various fluences of Ar+ implantation and then measured by the new method utilizing optical free carrier absorption (FCA) technique to assess the interface traps. A program has been developed using MATLAB to extract surface recombination velocity (SRV) at the oxide/epi-layer interface from the optical data. Capacitance-voltage (CV) is done to extract the density of interface traps (Dit) and a comparison was made. It is observed that SiO2 samples show a large rise of SRVs, from 0.5×104 cm/s for a reference sample to 8×104 cm/s for a fluence of 1×1012 cm-2, whereas Al2O3 samples show more stable SRV, changing from 3×104 cm/s for the un-irradiated reference sample to 6×104 cm/s for a fluence of 1×1012 cm-2. A very similar trend is observed for Dit values extracted from CV measurements and it can therefore be concluded that the FCA method is a suitable technique for the interface characterization.
Authors: Margareta K. Linnarsson, J. Isberg, Adolf Schöner, Anders Hallén
Abstract: The boron diffusion in three kinds of group IV semiconductors: silicon, silicon carbide and synthetic diamond has been studied by secondary ion mass spectrometry. Ion implantation of 300 keV, 11B-ions to a dose of 21014 cm-2 has been performed. The samples are subsequently annealed at temperatures ranging from 800 to 1650 °C for 5 minutes up to 8 hours. In silicon and silicon carbide, the boron diffusion is attributed to a transient process and the level of out-diffusion is correlated to intrinsic carrier concentration. No transient, out-diffused, boron tail is revealed in diamond at these temperatures.
Authors: Roberta Nipoti, Anders Hallén, Antonella Parisini, Francesco Moscatelli, Salvatore Vantaggio
Abstract: The p-type doping of high purity semi-insulating 4H-SiC by Al+ ion implantation and a conventional thermal annealing of 1950 °C/5 min has been studied for implanted Al concentration in the range of 1 x1019 - 8 x 1020 cm-3 (0.36 μm implanted thickness). Sheet resistance in the range of 1.6 x 104 to 8.9 x102 Ω, corresponding to a resistivity in the range of 4.7 x 10-1 to 2.7 x 10-2 Ωcm for increasing implanted Al concentration have been obtained. Hall carrier density and mobility data in the temperature range of 140–600 K feature the transition from a valence band to an intra-band conduction for increasing implanted Al concentration. The specific contact resistance of Ti/Al contacts on the 5 x1019 cm-3 Al implanted specimen features a thermionic field effect conduction with a specific contact resistance in the 10-6 Ωcm2 decade.
Authors: Margareta K. Linnarsson, Sethu Saveda Suvanam, Lasse Vines, Anders Hallén
Abstract: Relocation of alkali metals sodium, potassium and cesium during oxidation of 4H-SiC has been studied by secondary ion mass spectrometry. The alkali metal source has been introduced by ion implantation before oxidation into n-and p-type 4H-SiC samples. Dry oxidation of SiC has been performed at 1150 oC during 4, 8 and 16 h. In the formed oxide, the main part of the alkali metals diffuses out via the SiO2 surface. Close to the moving SiO2/SiC interface, a minor amount of alkali metals is retained. In the SiC material, the main amount of implanted alkali atoms is not redistributed during the oxidation, although a minor amount diffuses deeper into the samples. For p-type 4H-SiC, the diffusion deeper into the samples of the studied alkali metals decreases as the mass increases, Na+<K+<Cs+, but the sodium mobility is substantial already at 1150 °C.
Authors: John Österman, Srinivasan Anand, Margareta K. Linnarsson, Anders Hallén
Authors: Martin S. Janson, Anders Hallén, Phillippe Godignon, Andrej Yu. Kuznetsov, Margareta K. Linnarsson, Erwan Morvan, Bengt Gunnar Svensson
Authors: Andrej Yu. Kuznetsov, Martin S. Janson, Anders Hallén, Bengt Gunnar Svensson, C. Jagadish, H. Grünleitner, Gerhard Pensl
Authors: Muhammad Usman, T. Pilvi, Markku Leskelä, Adolf Schöner, Anders Hallén
Abstract: Aluminum-based high-k dielectric materials have been studied for their potential use as passivation for SiC devices. Metal-insulator-semiconductor structures were prepared and their dielectric properties were analyzed using capacitance-voltage and current-voltage measurements. Atomic layer deposition was used for the deposition of dielectric layers consisting of AlN with or without a buffer layer of SiO2, and also a stack of alternating AlN and Al2O3 layers. It has been observed that AlN has a polycrystalline structure which provides leakage paths for the current through the grain boundaries. However, adding alternate amorphous layers of Al2O3 prevent this leakage and give better overall dielectric properties. It is also concluded that the breakdown of the dielectric starts from the degradation of the thin interfacial SiO2 layer.
Authors: Maciej Wolborski, Mietek Bakowski, Viljami Pore, Mikko Ritala, Markku Leskelä, Adolf Schöner, Anders Hallén
Abstract: Aluminium oxide and titanium oxide films were deposited using the Atomic Layer Deposition method on n-type 4H SiC and p-type Si {001} substrates, with doping 6×1015cm-3 and 2×1016cm-3, respectively, and on 1.2 kV PiN 4H SiC diodes for passivation studies. The Al2O3 and SiC interface was characterised for the existence of an effective negative charge with a density of 1×1012-2×1012 cm-2. The dielectric constant of Al2O3 as determined from capacitance-voltage data was about 8.3. The maximum electric field supported by the Al2O3 film was up to 7.5 MV/cm and 8.4 MV/cm on SiC and Si, respectively.
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