Domain formation during syntaxy of polytypes of silicon carbide
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IC STRUCTURE AND NONELECTRONIC PROPERTIES OF SEMICONDUCTORS
Domain Formation During Syntaxy of Polytypes of Silicon Carbide D. D. Avrova^, S. I. Dorozhkina, A. O. Lebedevb, and Yu. M. Tairova aSt.
Petersburg State Electrotechnical University (LETI), ul. Popova 5, St. Petersburg, 197376 Russia ^e-mail: [email protected] bIoffe Physicotechnical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia Submitted April 18, 2007; accepted for publication April 23, 2007
Abstract—An algorithm for the search of a domain structure appearing in a growing single crystal of silicon carbide on the emergence of syntaxic inclusions is presented. Experimentally observed crystal joints are analyzed. PACS numbers: 61.72.Bb, 61.72.Dd, 61.72.Mm, 81.05.Hd, 81.10.Bk DOI: 10.1134/S1063782607120019
1. INTRODUCTION Silicon carbide is a wide-gap semiconductor with unique properties which make it useful in extreme electronics [1]. Silicon carbide is characterized by polytypism, or the existence of a large number of structural modifications differing in the character of the second or more remote coordination spheres [2]. Relatively small single crystals of silicon carbide can be obtained using sublimation of the SiC charge with the subsequent condensation by the classical seedless Lely method [3]. In addition, a substantial progress in the technology of this material is attained with the use of the LÉTI method (modified Lely method in foreign publications), which allowed researchers to increase the diameter of the grown crystals of silicon carbide to 4 (!) inches. However, as a rule, synthesized single crystals are characterized by a high density of structural defects, such as micropores, dislocations, low-angle boundaries, etc. One of the most often occurring defects in single crystals of silicon carbide, which are obtained by both methods, are foreign polytype inclusions, where, by unknown causes, local regions of another polytype modification emerge in the growing ingot [4, 5]. In some cases, polytype modifications sequentially force out each other over the entire growth surface, which leads to emergence of the so-called sandwich structures [5]. It will be shown below that the emergence of polytype inclusions should lead (and leads) to appearance of numerous domains in the growing single crystal. In this article, we present the algorithm for the search of the domain structure, which appears in the growing single crystal on emerging the syntaxy inclusions, and the experimentally observed crystal joints are analyzed.
2. EMERGENCE OF DOMAINS DURING SYNTAXY OF POLYTYPES. GENERAL APPROACH It will be shown below that the formation of polytype inclusion is accompanied by fulfillment of the condition for polycentricity of nucleation, which allows use of the approaches previously developed for epitaxial growth for the analysis of the domain structure in this case [6–8]. Let us consider the epitaxial growth system, which consists of the substrate (matrix of the main polytype) and epitaxial layer (polytype inc
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