Point defects in SiC

SiC is a wide-bandgap semiconductor that can withstand high power, high temperature, and high frequency, making it important for device applications and quantum technologies. It can exist in over 200 polytypes, determined by the stacking pattern of Si-C bilayers. However, its performance is strongly influenced by the presence of point defects. First-principles calculations on the thermodynamic stability of several common hexagonal structures (2H, 4H, 6H, 8H, 10H, and 12H) and cubic SiC reveal that the cubic and 10H polytypes have the lowest formation energy, whereas 4H and 6H have the second lowest. Further stability analysis indicates that the 4H structure is the most stable. We have studied several point defects, including Si and C monovacancies (V_Si and V_C), anti-site pairs, and Si and C interstitials (Sii and Ci) in 3C, 4H, and 6H structures. Our studies show that divacancies and NV centers are most stable in the spin S = 1 state. Of all these defects, only the carbon monovacancy in 6H-SiC forms spontaneously. V_Si and C_i, in particular, show deep defect levels in 4H-SiC, which aligns with observed experimental data.