Polytypes in bulk form were systematically investigated using an ab initio pseudopotential approach for the total energy calculations with/without vacancy in four structures such as 3C (zincblende), 6H, 4H, and 2H (wurtzite) structures. The calculated results revealed that 3C and 4H were favourable for SiC in contrast with 3C for Si and 2H for AlN. Furthermore, the energy differences ΔE among four structures for SiC were very small without explicit dependence on the hexagonality in contrast with the ΔE for AlN and Si without polytypes. The ΔE for SiC with vacancy revealed the most stable structures such as 6H with Si-vacancy and 4H with C-vacancy. This qualitatively agreed well with experimental results where 3C appeared at low temperatures while 6H and 4H were favoured at high temperatures enhancing vacancy formation. Furthermore, the calculated vacancy formation energies suggested that C-rich condition prefers 6H whereas 4H was favoured under Si-rich condition.

Theoretical Investigations of the Polytypism in Silicon Carbide: Contribution of the Vacancy Formation. T.Ito, T.Kondo, T.Akiyama, K.Nakamura: Physica Status Solidi C, 2011, 8[2], 583–5