EPR andab initiocalculation study on the EI4 center in4H- and6H-SiC

Abstract

We present results from electron paramagnetic resonance (EPR) studies of the EI4 EPR center in $4H$- and $6H\text{-SiC}$. The EPR signal of the EI4 center was found to be drastically enhanced in electron-irradiated high-purity semi-insulating materials after annealing at $700--750\text{ }\ifmmode^\circ\else\textdegree\fi{}\text{C}$. Strong EPR signals of the EI4 center with minimal interferences from other radiation-induced defects in irradiated high-purity semi-insulating materials allowed our more detailed study of the hyperfine (hf) structures. An additional large-splitting $^{29}\text{S}\text{i}$ hf structure and $^{13}\text{C}$ hf lines of the EI4 defect were observed. Comparing the data on the hf interactions and the annealing behavior obtained from EPR experiments and from ab initio supercell calculations of different carbon-vacancy-related complexes, we suggest a complex between a carbon vacancy-carbon antisite and a carbon vacancy at the third-neighbor site of the antisite in the neutral charge state, ${({V}_{\text{C}}{\text{-C}}_{\text{Si}}{V}_{\text{C}})}^{0}$, as a new defect model for the EI4 center.