ANALYSIS OF THE ELECTROLUMINESCENCE OBSERVED DURING THE ANODIC-OXIDATION OF POROUS LAYERS FORMED ON LIGHTLY P-DOPED SILICON

A detailed analysis of the different characteristics of the electroluminescence that is observed during the anodic oxidation of porous silicon layers formed on lightly p-doped substrates is presented. It is shown that the emission presents characteristics very similar to that of the photoluminescence observed on the same porous layers, and that the same basic mechanisms are involved in the two phenomena. The emission intensity increase with the oxidation level is quantitatively explained by the passivation enhancement provided by the electrochemical oxidation. The spectral shift of the spectra during the oxidation is also discussed: It is shown to result from the decrease in the sizes of the largest emitting crystallites or/and from the significant improvement of the passivation of the smallest ones due to the oxide growth. The effect of the anodizing current density on the emission efficiency is also presented.