6H and 4H-SiC Bulk Growth by PVT and Advanced PVT (APVT)
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J5.24.1
6H and 4H-SiC Bulk Growth by PVT and Advanced PVT (APVT) A. Gupta1, M. Yoganathan1, E. Semenas1, I. Zwieback1, E. Emorhokpor1, C. Martin1, T. Kerr1, A. Souzis1, T. Anderson1, J. Chen2, C. Tanner2, D. Barrett2, R. Hopkins2, and C. Johnson2 1
II-VI, Inc. 20 Chapin Rd, Suite 1005, Pine Brook, NJ 07058 USA 2 II-VI, Inc. 375 Saxonburg Blvd., Saxonburg, PA 16056 USA
ABSTRACT II-VI, Inc. is a commercial supplier of high-quality SiC substrates (including 2-inch and 3-inch diameter) for RF and power applications to the US market. Semi-insulating 6H-SiC single crystals, doped with vanadium and undoped (vanadium-free), as well as ntype 4H crystals have been grown using the PVT and Advanced PVT (APVT) growth techniques. The APVT process incorporates insitu synthesis and growth of of SiC crystal from Si and C precursors. Grown 6H-SiC and 4H-SiC crystals have been extensively characterized with respect to their purity, crystal quality and electrical properties. COREMA resistivity maps demonstrate that V-compensated boules exhibited axially and radially uniform resistivity around 1011 Ω·cm at room temperature. Undoped (V-free) wafers contained residual boron and nitrogen at levels below 1016 atoms/cm3, and demonstrated semi-insulating properties (resistivity between 106 and 1011 Ω·cm) as a result of compensation by native point defects with deep levels in the bandgap. The undoped semi-insulating crystals grown by APVT contained boron and nitrogen at 1.9·1015 cm-3 and 3.8·1015 cm-3, respectively. High-quality 2-inch SiC wafers exhibited micropipe densities on the order of 10 cm-2 and dislocation density on the order of 104 cm-2. INTRODUCTION Silicon carbide is an attractive material for the next generation of solid state radar and power switching devices. High power RF applications require semi-insulating SiC wafers with the electrical resistivity above 105 Ω-cm at room temperature. II-VI, Inc., develops and manufactures semi-insulating (V-doped and undoped) 6H-SiC and recently we have started marketing n-type 4H-SiC wafers. The presence of background impurities such as nitrogen and boron makes the production of semi-insulating SiC substrates a challenge. Therefore, the use of high purity source or a source with a compensating agent is necessary to produce semiinsulating SiC crystals. In this paper we focus on: a) synthesis of high purity source material, b) sublimation growth of SiC crystals, c) semi-insulating properties of vanadium-doped [1,2] and undoped 6H-SiC single crystal [3] and d) nitrogen doped 4HSiC. The crystals have been extensively characterized, and results of purity, crystal quality and electrical properties are presented.
J5.24.2
EXPERIMENTAL Synthesis of SiC is carried out by reacting silicon and carbon precursors at high temperatures. High purity source is critical for the growth of doped semi-insulating SiC crystals by PVT. N-type 4H-SiC crystals have been grown by the PVT technique combined with in-situ nitrogen doping. The APVT process [4] is used to grow undoped 6H-SiC crystals, which involves
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