Room-temperature 1.54 μm electroluminescence (EL) was compared for Au/SiO2:Er/n+-Si and Au/SiOx:Si:Er/n+-Si diodes under reverse bias. The 18 nm thick SiO2:Er and SiOx:Si:Er films were deposited by the magnetron sputtering technique. The maximum of the EL intensity was reached after annealing at 900 °C (SiO2:Er) and 800 °C (SiOx:Si:Er). The threshold potential of the EL was about 4 and 6 V for the Au/SiOx:Si:Er/n+-Si and Au/SiO2:Er/n+-Si diodes, respectively. The power efficiency was larger for the Au/SiOx:Si:Er/n+-Si diode than that for the Au/SiO2:Er/n+-Si diode by six times. Our experimental results demonstrate that the existence of Si nanoclusters reduces the threshold potentials of the EL and strongly enhances the power efficiency for Er3+ EL. © 2001 American Institute of Physics.