1.54  μm photoluminescence from Er:O_x centers at extremely low concentration in silicon at 300 K

The demand for single photon emitters at λ=1.54  μm, which follows from the consistent development of quantum networks based on optical fiber technologies, makes Er:O_x centers in Si a viable resource, thanks to the I_13/24→I4_15/2 optical transition of Er³⁺. While its implementation in high-power applications is hindered by the extremely low emission rate, the study of such systems in the low concentration regime remains relevant for quantum technologies. In this Letter, we explore the room-temperature photoluminescence at the telecomm wavelength from very low implantation doses of Er:O_x in Si. The lower-bound number of optically active Er atoms detected is of the order of 10², corresponding to a higher-bound value for the emission rate per individual ion of about 10⁴  s^-1.