第一原理による多形決定のメカニズム解明(<特集>SiCの現状と今後の展開)

概要

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Polytypism in semiconductors such as SiC and ZnS is systematically investigated using ab initio pseudopotential approach for the total energy calculations in four structures such as 3C (zinc blende), 6H, 4H, and 2H (wurtzite) structures with/without vacancies. Our calcualted energy differences ΔE among four structures without vacancy reveal that SiC favors 3C and 4H while 3C is preferred for ZnS. The ΔE for SiC with vacancy explicitly elucidates the most stable structures such as 6H with Si-vacancy and 4H with C-vacancy. On the other hand, ZnS with vacancy prefers 2H with S-vacancy. In particular, the calculated vacancy formation energies suggest that C-rich and Si-rich conditions respectively prefer 6H-SiC and 4H-SiC, while 2H-ZnS appears independent of the conditions. These results suggest that the vacancy formation plays an important role in the polytypism in semiconductors. Furthermore, nitrogen substituting for carbon and silicon in SiC respectively stabilizes 3C and 4H. It is found that the polytypism in semidonductors can be sytematically interpretted by considering difference in interatomic bond charges between before and after point defect formation.
2013-04-00