Polytypes in bulk form were systematically investigated using an ab initio pseudopotential approach for the total energy calculations with/without vacancies 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 to 3C for Si and 2H for AlN. Furthermore, the energy differences ΔE among four structures for SiC were very small, without any explicit dependence upon the hexagonality; in contrast to the ΔE for AlN and Si without polytypes. The ΔE for SiC with a vacancy revealed the most stable structures such as 6H with a Si-vacancy and 4H with a C-vacancy. This agreed qualitatively 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 favoured 6H whereas 4H was favoured by Si-rich conditions.

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