Correlation between electroluminescence and charge trapping in multi-color Eu-implanted Si-based light-emitting diodes

Electroluminescence (EL) spectra, charge trapping during operation of EL devices and clustering of rare earth oxides in SiO₂ have been investigated in Eu-implanted SiO₂-Si structures which demonstrate luminescence associated with the light-emitting transitions in Eu²⁺ and Eu³⁺. Strong electron trapping in all studied regions of the injected charge (from 1x10E¹⁴ to 1x10E¹⁸ e/cm²) during operation of the light-emitting devices has been found that considerably differed from the oxides implanted by other rare earth impurities (Ce, Tb, Gd, Er, Tm). It has been shown that the observed strong electron trapping and the low EL intensity in the Eu implanted structures were associated with enhanced clustering of the Eu oxides. The mechanisms of electron trapping in the SiO₂ containing a large cluster concentration is discussed, and flash lamp annealing is proposed to decrease the nanocluster size and to enhance the EL intensity.