Alphabet luminescence lines in4H−SiC

First-principles density functional calculations are used to investigate antisite pairs in $4H-\mathrm{SiC}.$ We show that they are likely to be formed in close proximity under ionizing conditions, and they possess a donor level and thermal stability consistent with the series of 40 photoluminescent lines called the alphabet lines. Moreover, the gap vibrational mode of the silicon antisite defect is close to a phonon replica of the $b_1$ line and possesses a weak isotopic shift with ${}^{13}\mathrm{C}$ in agreement with observation.