Electroluminescence from erbium-doped nanoscale pn diodes was achieved. Decreasing the number of erbium ions in scaling light-emitting silicon devices decreases the emission intensity. This trend opens new possibility of single-photon emission-key function of quantum communication. Furthermore, doping by ion implantation takes advantage of controlling the number and position of erbium ions in the device. According to this trend, we fabricated pn-diodes with dimensions of telecom wavelength and observed the electroluminescence from the erbium doped region at the forward bias of 1.2 V. We discuss the photoemissivity and the current-voltage characteristics of the device, toward the single-photon emission.