On the mechanism of electroluminescence excitation in Er-doped SiO2 containing silicon nanoclusters

The effect of the density of silicon nanoclusters on both electroluminescence (EL) and photoluminescence (PL) of Er3+ ions in indium-tin oxide/SiO2:Er/n-type silicon metal-oxide-semiconductor structures was studied by co-implantation of excess silicon into a 200 nm SiO2 layer with a concentration in the range of 1-15%. Contrary to the PL, the EL from both the green and infrared peaks of Er3+ shows a dramatic quenching when the average distance between the silicon clusters decreases below 3 nm. In addition, electric-field-induced quenching of the photoluminescence from silicon clusters and Er3+ is observed. These results indicate that the EL excitation process of Er3+ ions is governed by the direct impact excitation by hot electrons. An increase of the silicon nanocluster density causes direct tunneling of electrons between silicon clusters, thus reducing the population of energetic hot electrons for impact excitation of Er3+ ions.