Detection of Single W-Centers in Silicon

Controlling the quantum properties of individual fluorescent defects in silicon is a key challenge toward large-scale advanced quantum photonic devices. Research efforts have so far focused on extrinsic defects based on impurities incorporated inside the silicon lattice. Here, we demonstrate the detection of single intrinsic defects in silicon, which are linked to a tri-interstitial complex called the W-center, with a zero-phonon line at 1.218 μm. Investigating their single-photon emission properties reveals new information about this common radiation damage center, such as its dipolar orientation and its photophysics. We also identify its microscopic structure and show that, although this defect does not feature electronic states in the bandgap, Coulomb interactions lead to excitonic radiative recombination below the silicon bandgap. These results could set the stage for numerous quantum perspectives based on intrinsic luminescent defects in silicon, such as integrated quantum photonics and quantum communications.