Enhancement of porous silicon photoluminescence by NF3/UV photo-thermal surface treatment

A NF3/UV photo-chemical surface treatment of porous silicon is presented. T he UV photons are provided by an excimer lamp. This treatment strongly enha nces the photoluminescence of porous silicon. The increase of PL intensity is about 1-2 orders of magnitude at treatment temperatures in the range of 300-400 degrees C. Using AFM and Auger measurements, it is found that the P L enhancement can be correlated with the growth of about micron thick SiOx layer with the x value close to 2, and incorporation of fluorine. The overa ll effect of photoluminescence enhancement is suggested to be due to the NF 3/UV photothermal etching of the as-formed native oxide, as well as to the cleaning and passivation of the porous silicon surface with fluorine, follo wed by a rapid growth of a more stoichiometric oxide SiOx (x approximate to 2) layer in air.