First principles study of the T-center in Silicon

TL;DR

This study uses first principles calculations to analyze the electronic structure, stability, and optical properties of the T-center in silicon, revealing its potential for quantum technology due to its long-lived defect-bound exciton state.

Contribution

The paper provides the first detailed computational analysis of the T-center's electronic structure, stability, and radiative lifetime, highlighting its suitability for quantum applications.

Findings

The T-center forms a defect-bound exciton with a long microsecond radiative lifetime.

The T-center is stable against decomposition but sensitive to hydrogenation.

The localized defect state has strong carbon p-character, similar to ethyl radical localization.

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 \textit{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 $\mu$s, much longer 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 that the T-center is easily prone to (de)hydrogenation and so requires very precise annealing conditions (temperature and atmosphere) to be efficiently formed.