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First-Principles Study of N Impurities in SiC Polytypes

  • W. Windl (a1) and A. A. Demkov (a1)


We investigate theoretically the energetics of nitrogen impurities in β-SiC, their geometrical relaxation, and electronic properties. We find that density-functional theory is able to calculate donor-ionization energies accurately once large enough simulation cells are used. For neutral interstitial defects, we find that configurations where N is three-fold coordinated have very low formation energies and high binding energies with the involved native defects. At the same time, such configurations introduce deep levels into the gap which may result in a non-activation of the donor



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11. In reality, there exists no perfect stoichiometry for SiC crystals; therefore, the appropriate reference reservoirs are bulk Si and SiC for the Si-rich, and graphite and bulk SiC for the C-rich compound. Therefore, depending on the composition, the formation energies have to be adjusted by adding/subtracting the appropriate multiples of theβ-SiC cohesive energy of ECoh∼ 0.7 eV (the formation energy of a vacancy (anti-site) at a majority site, e.g., should be increased by Ecoh (2Ecoh), etc.). See, e.g., Ref. 1.


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