Localized states and porous silicon luminescence

Through photomodulated infrared and photoluminescence spectroscopies, electronic states of photocarriers in porous silicon have been investigated. The infrared spectrum of photogenerated carriers is drastically affected by their localization. Results are reported for porous silicon left in the HF solution in which it has been fabricated (wet porous silicon), for porous silicon just after immersion from the previous solution (dry porous silicon), or for porous silicon anodically oxidized in a non fluoride electrolyte just after its fabrication, and then taken out from the electrolyte (oxidized porous silicon).