Evidence that blue luminescence of oxidized porous silicon originates from SiO2

Abstract

We have analyzed red and blue luminescence from porous silicon as a function of oxidation parameters and feature dimension determined with an atomic force microscope. We have found correlation between blue luminescence intensity and the increase in feature size caused by oxidation. We have further shown that blue luminescence, is identical, with respect to spectrum and fast decay, to that of high microelectronic quality SiO₂ grown on crystalline silicon using dry oxygen plus an organic chlorine compound. Thus, we conclude that blue luminescence originates from SiO₂ film rather than from the silicon nanocrystals in the porous material. Intensity enhancement, as compared to SiO₂ on crystalline wafers, comes from the gigantic surface area of porous silicon.