First-principles calculations on quantum defects in silicon

Silicon is an excellent platform for quantum defects owing to the advanced growth and fabrication techniques readily available in this material, offering an ideal environment for the spin and optical properties of the hosted defects. Moreover, several known emitter defects in silicon operate in the telecommunication wavelengths. The recent experimental advancements in the isolation and manipulation of these defects calls for an in-depth identification using high level first-principles calculations.

My presentation will detail the recent computational advancements for three promising emitter defects in silicon, the so-called W, G and C photoluminescence (PL) centers. We identify the origin of the W PL-line as an excitonic recombination originating from the tri-interstitial silicon defect complex, which produces no in-gap states in its neutral charge state. For the identification of the G-center, we combine the conventional HSE+U density functional theory with GW perturbation method. We also show that the formation of the most stable configuration of this defect is kinetically hindered, thus demonstrating that high-throughput searches might overlook key candidates. Moreover, this defect shows an exotic rotational reorientation offering rich physics to explore. Finally, we propose the C-center as an L-band emitter with quantum memory feasible in its excited triplet spin state. We determine the excitonic nature of the emission using GW Bethe-Salpeter-equation calculations and establish the possible intersystem crossing paths between the singlet emitter manifold and the triplet qubit state.