PHOTO-ASSISTED EVOLUTION OF THE PHOTOLUMINESCENCE SPECTRUM OF POROUS SILICON IMMERSED IN HYDROFLUORIC-ACID

Rapid changes in photoluminescence (PL) intensity and blue shifts of t ypically 100 nm have been measured for porous silicon wetted by hydrof luoric acid. The differences between continuous and interrupted PL exc itation show that the process is not solely limited by photoactivation . In contrast, the effect of potassium hydroxide, a second silicon etc hant, is to reduce PL intensity without any significant blue shift. Th ese experiments show the importance of surface chemistry in PL of wet porous silicon and are interpreted in terms of surface termination by different species.