Divacancy in 3C- and 4H-SiC: An extremely stable defect

Article

关键词: NEGATIVE-U CENTERS;    AB-INITIO;    ELECTRONIC-STRUCTURE;    MOLECULAR-DYNAMICS;    FORMATION ENERGIES;    SILICON VACANCY;    NATIVE DEFECTS;    SPIN-DENSITY;    PHOTOLUMINESCENCE;    POSITRON;   

DOI  :  10.1103/PhysRevB.65.085202

来源: SCIE

【 摘 要 】

Using first-principles calculations for divacancy defects in 3 C- and 4H-SiC, we determine their formation energies and stability, their ionization levels, and relaxed geometries (symmetry point groups) for neutral as well as for charged states. For 4H-SiC all four possible, nearest-neighbor divacancy configurations are considered. We find not only a remarkable high binding energy of about 4 eV, but also a strong site dependence (cubic or hexagonal lattice sites) of the formation energies. Applying a Madelung-type correction to deal with the electrostatic interactions between charged supercells, our results indicate a negative-U behavior at E-v + 0.7 eV between the charge states 1 + /1 - only for nearest-neighbor divacancies on different lattice sites (mixed cubic and hexagonal) in 4H-SiC, but not for all the other cases (pure cubic or pure hexagonal) in 4H- or for the cubic divacancy in 3C-SiC.

【 授权许可】

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