Characterization of Highly Concentrated Bi Donors Wire-$\delta$-Doped in Si

We studied the Bi wire-$\delta$-doping process to achieve a high concentration of Bi donors in Si. Our process has two steps: (i) burial of Bi nanowires in Si by molecular beam epitaxy, and (ii) activation of Bi atoms in the $\delta$-doped layer by laser annealing. The peak concentration of Bi atoms in the $\delta$-doped layer is controlled by two parameters: the coverage of surfactant layer, and the growth temperature during the Si cap-layer growth, whose maximum concentration is larger than $10^{20}$ cm -3 . Photoluminescence and electrical carrier transport measurements reveal that dense Bi atoms are activated upon heating the area at close to the melting point of Si. As a result, our doping process results in Bi donors in the wire-$\delta$-doped layer with concentration of ${>}10^{18}$ cm -3 . This will be useful for establishing next-generation, quantum information processing platform.