Hybrid Functional Study on the Intrinsic Defect, Extrinsic <i>n</i>- and <i>p</i>-type Doping in 6H-SiC

6H-SiC has garnered significant attention due to its promising applications in high-power devices and high-temperature sensors. However, the presence and properties of intrinsic defects that could significantly impact the material’s performance and the mechanisms of n-type (N, P, and As) and p-type (B, Al, and Ga) doping and their performance optimization remain unclear. In this work, we conduct a comprehensive investigation into the intrinsic defect physics of 6H-SiC and assess the effects of both intentional n-type (Group VA) and p-type doping (Group IIIA) on its conductivity, electronic structure, and optical properties. Our findings reveal that intrinsic defects in 6H-SiC generally exhibit high formation energies and deep transition levels, making their impact on conductivity minimal. Most of them should only form under nonthermal equilibrium growth conditions, such as high-temperature annealing and strong radiation. Furthermore, most of these intrinsic defects will also introduce defect energy levels in the band gap, which could act as the trapping centers of the photogenerated electrons or the recombination centers of the photogenerated electron–hole pairs. Particularly, for n-type doping, N and P emerge as ideal dopants, with N yielding excellent n-type 6H-SiC under C-poor conditions and P showing optimal performance in C-rich environments. In contrast, among the p-type dopants, Al stands out as the only excellent and ideal dopant, demonstrating a superior p-type doping efficiency under Si-poor conditions. The p-type doping of B shows significantly less favorable results compared to the n-type doping of N, which may be related to the intrinsic donor property of the carbon vacancy in 6H-SiC. These findings enhance our understanding of the defect physics in 6H-SiC and offer valuable insights for developing and optimizing high-performance 6H-SiC materials.