Aluminum and boron diffusion in 4H-SiC
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Aluminum and boron diffusion in 4H-SiC M.K. Linnarsson1, M.S. Janson1, A. Schöner2 and B.G. Svensson1,3 1 Royal Institute of Technology, Solid State Electronics, P.O. Box E229, SE-164 40 KistaStockholm, Sweden 2 ACREO AB, P.O. Box E236, SE-164 40 Kista-Stockholm, Sweden 3 University of Oslo, Department of Physics, Physical Electronics, P.B. 1048 Blindern, N-0316 Oslo, Norway
ABSTRACT A brief survey is given of some recent result of boron diffusion in low doped n-type (intrinsic) and p-type 4H-SiC. Aluminum diffusion and solubility limit in 4H-SiC are also discussed. Ion implantation of boron has been performed in epitaxial material to form a diffusion source but also epitaxial 4H-SiC structures, with heavily boron or aluminum doped layers prepared by vapor phase epitaxy have been studied. Heat treatments have been made at temperatures ranging from 1100 to 2050°C for 5 minutes up to 64 h. Secondary ion mass spectrometry has been utilized for analysis. For boron diffusion in acceptor doped 4H-SiC, 4x1019 Al atoms/cm3, an activation energy of 5.3 eV has been determined and a strong dependence on Al content for the diffusion coefficient is revealed. Transient enhanced diffusion of ion-implanted boron in intrinsic 4H-SiC samples is discussed. Solubility limits of ~1x1020 Al/cm3 (1700°C) and 104 cm-2 compared to dislocation free crystals (ρ
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