First-principles identification of deep energy levels of sulfur impurities in silicon and their carrier capture cross sections

Studies of the deep energy levels and nonradiative carrier capture induced by sulfur doping in silicon were initiated 60 years ago; however, the defect configurations, their deep energy levels, and the carrier capture cross sections are still not well understood. In this study, we focus on SSi substitution, and perform a first-principles study of its defect configurations and the deep energy levels using hybrid exchange-correlation functional. We discover a new distortive configuration for SSi+ besides the previously obtained structure with higher symmetry. For both SSi+ configurations, the deep transition levels (0/+) and (+/2+) are determined as 0.35 eV and 0.68 eV below the conduction band minimum, respectively. As a benchmark calculation, the hole-capture cross sections for neutral and +1 charged states are obtained based on the distortive structure. The cross section for SSi+ agrees with the experiment, demonstrating the multi-phonon process for SSi+ capturing a hole, whereas the cross section of SSi0 is significantly lower than the experimental data because hole capture by SSi0 is an Auger-type process. Our calculations provide a benchmark for the evaluation of the cross section of carrier capture in semiconductors using multi-phonon nonradiative recombination theory.