  Special point defects in semiconductors have been envisioned as suitable
components for quantum-information technology. The identification of new deep
centers in silicon that can be easily activated and controlled is a main target
of the research in the field. Vacancy-related complexes are suitable to provide
deep electronic levels but they are hard to control spatially. With the spirit
of investigating solid state devices with intentional vacancy-related defects
at controlled position, here we report on the functionalization of silicon
vacancies by implanting Ge atoms through single-ion implantation, producing
Ge-vacancy (GeV) complexes. We investigate the quantum transport through an
array of GeV complexes in a silicon-based transistor. By exploiting a model
based on an extended Hubbard Hamiltonian derived from ab-initio results we find
anomalous activation energy values of the thermally activated conductance of
both quasi-localized and delocalized many-body states, compared to conventional
dopants. We identify such states, forming the upper Hubbard band, as
responsible of the experimental sub-threshold transport across the transistor.
The combination of our model with the single-ion implantation method enables
future research for the engineering of GeV complexes towards the creation of
spatially controllable individual defects in silicon for applications in
quantum information technologies.
