Point defects in SiC

Point defects in silicon carbide (SiC) play a significant role in electronic devices and can be used as qubits in quantum computing. SiC exists in more than 200 polymorphs, defined by the stacking pattern of silicon-carbon layers. Here, we will present our calculation of the thermodynamic stability of cubic and several common hexagonal SiC structures, including 2H, 4H, 6H, 8H, 10H, and 12H. We found that the cubic and 10H structures are the most stable, followed by 4H and 6H. Although 10H, 6H, and 4H-SiC have similar formation energies, cleaving energy analysis shows that 4H-SiC is the most stable because it resists cleaving across the c-axis better than the others. We also studied several point defects, such as silicon vacancies (V_Si), carbon vacancies (V_C), antisite doping, and both silicon and carbon interstitials (Si_i and C_i), in 3C, 4H, and 6H structures. V_Si and C_i, in particular, showed deep defect levels in 4H-SiC, which aligns with observed experimental data.