Deterministically Implanted Arrays of Donor Spin Qubits

Donor atoms in isotopically enriched silicon (²⁸Si) are promising for encoding quantum information due to their long spin coherence times and established coupling methods between donor nuclei. Antimony (Sb) donors further offer high-spin nuclei access to a higher dimensional hilbert space. Sb donors are introduced via ion implantation, but this process results in a random distribution of timed donor implants with inherent uncertainty in final donor location. For scaling qubit systems to multiple arrays of implanted donor atoms, high precision in donor placement through deterministic ion implantation is essential. To detect single implantation events, on-chip reverse-biased detector electrodes and p-i-n diodes are used to detect charge carriers generated by single counted implantation events. Previously, implantation of single low-energy (14 keV) donor ions with detection fidelity of 99.87% has been reported.

Here we propose a plan for integrating on-chip detectors with donor qubit devices, comparing in-plane (lateral) and sandwich (vertical) detector designs for optimal charge collection and detection fidelity. An AFM nanostencil used for donor implantation may misalign by ~100 nm with respect to EBL defined alignment markers; however implanting high-fluence Sb atoms in corner pixels aids in locating donor arrays during device fabrication. Finally, spin chains are fabricated to characterize the uniformity of the ordered implanted donor arrays through excitation spectra analysis.