IN-SITU LUMINESCENCE AND IR STUDY OF POROUS SILICON DURING AND AFTER ANODIC-OXIDATION

When porous silicon is transferred into a non-fluoride electrolyte and anodically oxidized, the onset of red electroluminescence during anod ic oxidation appears correlated with a decrease in the OH IR absorptio n bands, indicating significant electrolyte removal from the ports. Th e electron states whose population is affected by carrier injection or light excitation have been investigated using in situ electromodulate d or photomodulated IR spectroscopy. The modulated IR absorption of re d-luminescent electro-oxidized porous silicon exhibits an extra absorp tion of localized carriers in the 1000-2500 cm(-1) region, suggesting that the red luminescence occurs through carriers trapped in localized states. The localization process may be efficiently affected by the d ielectric constant of the medium surrounding the silicon nanocrystalli tes.