On the Structural Perfection of Large-Diameter Silicon Carbide Ingots
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he Structural Perfection of Large-Diameter Silicon Carbide Ingots Yu. O. Bykova, *, A. O. Lebedeva, b, and M. P. Shcheglovb aSt. bIoffe
Petersburg State Electrotechnical University (LETI), St. Petersburg, 197376 Russia Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia *e-mail: [email protected] Received March 2, 2020; revised April 2, 2020; accepted April 10, 2020
Abstract—4H-silicon carbide ingots with high structural perfection have been grown by the modified Lely method (LETI method) on 100-mm-diameter seeds. Using our experimental data and theoretical analysis, we have systematized the key factors responsible for the degradation of the crystal structure of the ingots during the growth process. The formation of parasitic polytype inclusions in the early stages of growth has been shown to lead to the formation of antiphase boundaries and a mosaic substructure in the ingot. Keywords: silicon carbide, LETI method, defects, structural perfection DOI: 10.1134/S0020168520090034
INTRODUCTION Silicon carbide is used in the manufacture of highpower, high-frequency, and high-temperature electronic devices [1]. Single-crystal silicon carbide ingots are usually prepared by sublimation growth on SiC seeds (modified Lely method, or LETI method) in vacuum or an inert gas (usually in argon) at a temperature on the order of 2000°C or above [2]. An important feature of silicon carbide is its ability to crystallize in a large number of closely related structures, socalled polytypes [3]. At present, the number of known SiC polytypes exceeds 200, but only two of them, 4H and 6H, are used to grow large-diameter ingots on a commercial scale. To grow ingots of the 4H and 6H polytypes, use is made of seeds with the (000 1 )C and (0001)Si crystallographic orientations, respectively. Since the polytypes are similar in parameters, ingots often contain parasitic polytype inclusions, which lead to degradation of the single crystals [4]. In particular, ingots of the 4H polytype typically contain inclusions of the 6H, 15R, and 3C polytypes (the last is encountered at relatively low temperatures,
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