Crystal free energy of SiC polytypes and stacking faults formation energy from DFT-based lattice-dynamics approach.

Despite a rising impact of SiC technology in the power electronics industry, some fundamental aspects of this material lack physical understanding. Particularly polytypism and growth of SiC polytypes have been discussed as a paradox from about thirty years because of an evident discrepancy between theory and experiments, not yet elucidated. SiC has more than 200 polytypes and few of them (i.e. 3C, 6H, 4H) are commercially available and used for power devices. Besides the scientific interest, investigating SiC polytypism and understanding its driving force is crucial to correctly predict the energetics of extended defects in SiC, which are one of the main concerns of this wide band gap semiconductor. We perform first-principle calculations, including long range interactions and based on a lattice dynamics approach, we predict the temperature dependent thermodynamic stability of different SiC polytypes which may explain their growth at different temperature. Finally, we estimate the formation energy of stacking faults in SiC and the effect of Van Der Waals corrections are proved to be key for reproducing experimental observations.