Papers by Keyword: Bulk Growth

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Authors: Peter J. Wellmann, Katja Konias, Philip Hens, Rainer Hock, Andreas Magerl
Abstract: This work reports on the in-situ observation of a polytype switch during physical vapor transport (PVT) growth of bulk SiC crystals by x-ray diffraction. A standard PVT reactor for 2” and 3” bulk growth was set up in a high-energy x-ray diffraction lab. Due to the high penetration depth of the high-energy x-ray beam no modification of the PVT reactor was necessary in order to measure Laue diffraction patterns of the growing crystal with good signal to noise ratio. We report for the first time upon the in-situ observation of polytype switching during SiC bulk PVT growth.
Authors: Yuichiro Tokuda, Jun Kojima, Kazukuni Hara, Hidekazu Tsuchida, Shoichi Onda
Abstract: Our latest results of SiC bulk growth by High-Temperature Gas Source Method are given in this paper. Based on Mullins-Sekerka instability, optimal growth conditions to preclude dendrite crystals, which are one of the pending issues for high-speed bulk growth, was studied. First, the simulation studies showed that high temperature gradient in a growing crystal is required for high-speed bulk growth without dendrite crystals. Second, high-speed bulk growth was demonstrated under high temperature gradient.
Authors: J.H. Edgar, L.H. Robins, S.E. Coatney, L. Liu, J. Chaudhuri, K. Ignatiev, Z. Rek
Authors: Darren M. Hansen, Gil Chung, Mark J. Loboda
Abstract: A detailed understanding of the incorporation of N2 gas during PVT growth of SiC is required to achieve high performance, low resistivity n+ SiC substrates necessary for power device applications. In this report, nitrogen incorporation is investigated for growth of 4H SiC crystals from 2” to 3” diameter in conditions ranging from unintentionally doped to low resistivity (0.015 - cm). For a wafer in a particular boule a resistivity uniformity of ± 5% is typical although the uniformity decreases when the wafer orientation is cut off axis from the bulk growth direction. Within a boule growth, the nitrogen incorporation is found to be a function of growth time. As growth continues, the resistivity of wafers cut further from the seed increases. A typical 3” on axis sliced wafer has a within wafer resistivity uniformity of 5% compared with an average seed to tail variation of 10%. Due to the axial resistivity gradient the within wafer resistivity uniformity of off axis sliced wafers is 8%. These axial and radial gradients are thought to be a function of the changing C/Si ratio during growth. Nitrogen incorporation as a function of PVT geometry, N2 partial pressure, and growth temperature are investigated and discussed. In particular, nitrogen incorporation is found to depend on the crucible size and nitrogen partial pressure, but is not strongly dependent on the absolute growth temperature, for growth temperature ranging over 150°C. Modeling of PVT growth shows the axial resistivity gradient can be linked with a change in the C/Si ratio versus time. Trends and N2 gas incorporation behavior will be discussed using resistivity mapping, SIMS, and Hall effect data.
Authors: Thomas L. Straubinger, Matthias Bickermann, Michael Rasp, Roland Weingärtner, Peter J. Wellmann, Albrecht Winnacker
Authors: Philip Hens, Ulrike Künecke, Peter J. Wellmann
Abstract: We present p-type doping of bulk SiC crystals by the modified physical vapor transport (M-PVT) technique using TMA (Tri-Methyl-Aluminum). Using TMA as a dopant precursor allows a quite well defined crystal growth process control. The issue of improvement of conductivity (reduction of substrate resistivity) by reduction of unintentional acceptor compensation by nitrogen is addressed. It is shown that a decrease of compensation from approx. 3%...10% to approx. 0.5%...2.5% leads to a charge carrier mobility and, hence, conductivity increase of about factor two.
Authors: Hiroyuki Matsunami
Authors: Hiromasa Suo, Kazuma Eto, Tomohisa Kato, Kazutoshi Kojima, Hiroshi Osawa, Hajime Okumura
Abstract: The growth of n-type 4H-SiC crystal was performed by physical vapor transport (PVT) growth method by using nitrogen and aluminum (N-Al) co-doping. Resistivity of N-Al co-doped 4H-SiC was as low as 5.8 mΩcm. The dislocation densities of N-Al co-doped substrates were evaluated by synchrotron radiation X-ray topography (SXRT). In addition, epitaxial growth was performed on the N-Al co-doped substrates by chemical vapor deposition (CVD). No double Shockley type stacking fault was observed in the epitaxial layer.
Authors: Laurence Latu-Romain, Didier Chaussende, Carole Balloud, Sandrine Juillaguet, L. Rapenne, Etienne Pernot, Jean Camassel, Michel Pons, Roland Madar
Abstract: Because of the formation of DPB (Double Positioning Boundary) when starting from a hexagonal <0001> seed, DPB-free 3C-SiC single crystals have never been reported up to now. In a recent work we showed that, using adapted nucleation conditions, one could grow thick 3C-SiC single crystal almost free of DPB [1]. In this work we present the results of a multi-scale investigation of such crystals. Using birefringence microscopy, EBSD and HR-TEM, we find evidence of a continuous improvement of the crystal quality with increasing thickness in the most defected area, at the sample periphery. On the contrary, in the large DPB-free area, the SF density remains rather constant from the interface to the surface. The LTPL spectra collected at 5K on the upper part of samples present a nice resolution of multiple bound exciton features (up to m=5) which clearly shows the high (electronic) quality of our 3C-SiC material.
Authors: Didier Chaussende, Frédéric Mercier, Roland Madar, Michel Pons
Abstract: We have investigated through birefringence microscopy, a set of 3C-SiC crystals grown with the CF-PVT process, starting from different seeds and under different growth conditions. Through self nucleation experiments, the stable growth of very high quality 3C-SiC crystals at high temperature (2100°C) and at high rate (roughly 0.2 mm/h) is demonstrated. The possibility to develop bulk growth of 3C-SiC crystals is discussed.
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