Chemical Treatment after Annealing Enhances Photoluminescence from Porous Silicon

A silicon wafer was anodized to form porous silicon and then annealed followed by a chemical treatment. Annealed porous silicon has little efficiency of photoluminescence. The chemical treatments yielded photoluminescence at around 850 nm. The IR and ESR spectra showed that annealing forms silicon oxide with Pb-center and a-center levels, which results in the suppression of photoluminescence. After the chemical treatment, silicon oxide was removed and the two kinds of centers are disappeared. It possibly enhanced the photoluminescent efficiency. Further chemical treatment showed a blue shift of the photoluminescence. These results well support a quantum effect and suggest that the two kinds of centers in oxide are a factor of suppressing photoluminescence.