All‐Epitaxial Self‐Assembly of Silicon Color Centers Confined Within Sub‐Nanometer Thin Layers Using Ultra‐Low Temperature Epitaxy

Silicon‐based color‐centers (SiCCs) have recently emerged as quantum‐light sources that can be combined with telecom‐range Si Photonics platforms. Unfortunately, using conventional SiCC fabrication schemes, deterministic control over the vertical emitter position is impossible due to the stochastic nature of the required ion‐implantation(s). To overcome this bottleneck toward high‐yield integration, a radically innovative creation method is demonstrated for various SiCCs with excellent optical quality, solely relying on the epitaxial growth of Si and C‐doped Si at atypically‐low temperatures in an ultra‐clean growth environment. These telecom emitters can be confined within sub‐nm thick epilayers embedded within a highly crystalline Si matrix at arbitrary vertical positions. Tuning growth conditions and doping, different well‐known SiCC types can be selectively created, including W‐centers, T‐centers, G‐centers, and, especially, a so far unidentified derivative of the latter, introduced as G′‐center. The zero‐phonon emission from G′‐centers at ≈1300 nm can be conveniently tuned by the C‐concentration, leading to a systematic wavelength shift and linewidth narrowing toward low emitter densities, which makes both, the epitaxy‐based fabrication and the G′‐center particularly promising as integrable Si‐based single‐photon sources and spin‐photon interfaces. Solid‐state color center emitter formation by ion implantation has the drawback that emitter positions below the surface cannot be deterministically controlled on the nanoscale. Here, this bottleneck can be overcome by a fabrication scheme that departs from ion implantation and only uses epitaxial self‐assembly of color centers. Their formation can be controlled in layers as thin as one lattice constant.