First principles study of the T-center in Silicon

Abstract

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

Effect of Localization on Photoluminescence and Zero-Field Splitting of Silicon Color Centers

“…Excited state calculations for each defect are preformed by manually constraining the orbital occupations to excite one electron into an unoccupied band. Such an approach has been successfully used in combination with hybrid functionals to study the excited state properties of the nitrogen-vacancy (NV) defect in diamond [37], as well as various silicon defects [4,12,24].…”

“…In particular, a deeper understanding is needed of the electronic defect levels within the bulk silicon gap and the nature of the local states corresponding to these levels. In this work, we present a theoretical study of the electronic properties of the G-center [4][5][6][7][8], W-center [9][10][11], and T-center [12,13], which have been experimentally observed to have a dominant zero-phonon line within or near the telecommunication bands for low loss transmission of photons through optical fibers. Using a combination of first-principles calculations and tight-binding models, we present calculations of the band structures, photoluminescence spectra, and zero-field splitting (ZFS) parameters, and discuss them in relation to recent experimental results.…”