The (SiO2:Er/Si/SiO2:Er) nanometer sandwich structure, in which the thickness of the Si layer between the two SiO2:Er barriers was varied from 1.0 to 4.0 nm with an interval of 0.2 nm, was deposited on both n+-Si and p-Si substrates using the magnetron sputtering technique. Electroluminescence (EL) from the Au/(SiO2:Er/Si/SiO2:Er) nanometer sandwich /n+-Si diodes under reverse biases has been observed. The EL spectrum of each diode can be fitted by three Gaussian bands with peak energies of 0.757 eV (1.64 μm), 0.806 eV (1.54 μm), and 0.860 eV (1.44 μm), and full widths at half maximum of 0.052 eV, 0.045 eV, and 0.055 eV, respectively. The marked effect of the nanometer Si layer with suitable thickness on enhancing the EL from the Er3+ in the SiO2 layers has been demonstrated. Among the diodes with Si layers having various thicknesses, the intensities of the 1.64-, 1.54-, and 1.44-μm bands of the diode with a 1.6-nm Si layer attain maxima which are 22, 8, and 7 times larger than those of the control diode without any Si layer, respectively. © 2002 American Institute of Physics.