α -Al2O3의 이종 원자가 치환 결함에 대한 이론적 연구

초록

α-Al2O3 is a representative insulating material used in switching devices, power semiconductors, and gate dielectrics owing to its excellent electrical insulation, thermal stability, and chemical robustness. However, aliovalent impurities can introduce electrically active defect states and thermally activated carriers, thereby degrading its insulating performance even at low concentrations. Here, we theoretically investigate aliovalent substitutional defects in α-Al2O3 by analyzing defect-induced electronic-structure changes and defect formation energies. Mg and Si were considered as substitutional impurities at Al sites, while N and F were introduced at O sites. Al-site substitutions are favored under O-rich conditions, whereas O-site substitutions are favored under O-poor conditions. The formation-energy diagrams identify SiAl and FO as donor-type defects and MgAl and NO as acceptor-type defects. Transition-level analysis shows that SiAl, FO, and MgAl can act as carrier sources and may contribute to insulation degradation, whereas NO forms a deep acceptor level and is expected to have a smaller effect. These findings provide an atomistic understanding of impurity-induced degradation mechanisms and offer theoretical guidance for defect control in high-reliability α-Al2O3-based insulating materials.

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