First-principles study of the T center in silicon

The T center in silicon is a well-known carbon-based color that has been recently considered for quantum technology applications. Using first-principles computations, we show the excited state formed by defect-bound exciton made of localized defect occupied an electron to which hole bound. strong carbon $p$ character and reminiscent localization unpaired ethyl radical molecule. radiative lifetime calculated be on order microseconds, much longer than other defects such as nitrogen vacancy diamond agreement with experiments. associated small transition dipole moment result very different nature delocalized states forming exciton. Finally, use calculations assess stability center. We find stable against decomposition into simpler when keeping stoichiometry fixed. However, identify easily prone (de)hydrogenation so requires precise annealing conditions (temperature atmosphere) efficiently formed.