First-principles study of electronic and diffusion properties of intrinsic defects in 4H-SiC

As a wide bandgap semiconductor, SiC holds great importance for high temperature and high power devices. It is known that the intrinsic defects play key roles in determining the overall electronic properties of semiconductors; however, a comprehensive understanding of the intrinsic defect properties in the prototype 4H-SiC is still lacking. In this study, we have systematically investigated the electronic properties and kinetic behaviors of intrinsic point defects and defect complexes in 4H-SiC using advanced hybrid functional calculations. Our results show that all the point defects in 4H-SiC have relatively high formation energies, i.e., low defect concentrations even at high growth temperatures. Interestingly, it is found that the migration barriers are very high for vacancies (>3 eV) but relatively low for interstitial defects (∼1 eV) in SiC. Meanwhile, the diffusion energy barriers of defects strongly depend on their charge states due to the charge-state-dependent local environments. Furthermore, we find that VSi in SiC, a key defect for quantum spin manipulation, is unstable compared to the spin-unpolarized VC–CSi complex in terms of the total energy (under p-type conditions). Fortunately, the transformation barrier from VSi to VC–CSi is as high as 4 eV, which indicates that VSi could be stable at room (or not very high) temperature.