The shallow donor in zinc oxide (ZnO) is a promising semiconductor spin qubit
with optical access. Single indium donors are isolated in a commercial ZnO
substrate using plasma focused ion beam (PFIB) milling. Quantum emitters are
identified optically by spatial and frequency filtering. The indium donor
assignment is based on the optical bound exciton transition energy and magnetic
dependence. The single donor emission is intensity and frequency stable with a
transition linewidth less than twice the lifetime limit. The isolation of
optically stable single donors post-FIB fabrication is promising for optical
device integration required for scalable quantum technologies based on single
donors in direct band gap semiconductors.Comment: E. R. Hansen and V. Niaouris contributed equally to this work. 13
pages, 11 figure