Isotopically Selected Co-Doping of ¹²¹Sb and ¹²³Sb Pairs in Silicon

A reliable route to the deterministic fabrication of impurity ion donors in silicon is required to advance quantum computing architectures based upon such systems. This paper reports the ability to dope isotopically-defined unique (¹²¹Sb¹²³Sb)²⁺ molecular ions into silicon with measured detection efficiencies of 94% being obtained. Atomically resolved imaging of the doped Sb ions reveals substitutionally incorporated atoms with a Sb-to-Sb separation of ≈2 nm post-implantation, thus indicating suitability to form coupled qudit systems. Molecular dynamics simulations support the preference for doped Sb atoms to occupy lattice sites, driven by fast (≈1s) re-crystallization of localized ion implantation induced damage at 300 K. The Sb doping method used is fully compatible with integration into processing that includes pre-enrichment of the silicon host to sub-3 ppm ²⁹Si levels. As such, we present a potential pathway to the creation of scaled qudit arrays within silicon platforms for quantum computing.