Atomistic simulations on the thermal stability of the antisite pair in 3C- and 4H-SiC

Abstract

The thermal stability of the first-neighbor antisite pair configurations in 3C- and 4H-SiC is investigated by atomic-level computer simulations. First, the structure and energetics of these defects are determined in order to check the accuracy of the interatomic potential employed. The results are comparable to literature data obtained by the density-functional theory. Then, the lifetime of the antisite pair configurations is calculated for temperatures between 800 and $2500\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. Both in 3C- and 4H-SiC, the thermal stability of the antisite pairs is rather low. Therefore, in contrast to previous theoretical interpretations, the antisite pair cannot be correlated with the ${\mathrm{D}}_{\mathrm{I}}$ photoluminescence center that is stable to above $2000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The atomic mechanism of the recombination of the antisite pair in 3C-SiC and of three antisite pair configurations in 4H-SiC is a modified concerted exchange. Because of the different sizes of the silicon and carbon atoms, this process is not identical to the concerted exchange in Si. Two intermediate metastable configurations found during the recombination are similar to the bond defect in Si. Since the SiC lattice contains two types of atoms, there are also two different types of bond defects. The two bond defects can be considered as the result of the incomplete recombination of a carbon vacancy and a neighboring mixed dumbbell interstitial. The antisite pair in 4H-SiC with the two atoms on hexagonal sites has a slightly higher formation energy than the other three antisite pair configurations in 4H-SiC. Its lifetime shows another dependence on the temperature, and its recombination is characterized by a separate motion of atoms. The comparison to results obtained by molecular dynamics simulations that are based on the density-functional theory demonstrates that the atomistic simulations describe the antisite pair and its recombination reasonably well.