Abstract: The formation of photoluminescent porous silicon layers (PSL) in HF-HKO₃ based solution is reported,Photomicroscopy and scanning electron microscopy (SEM) reveal that the etched Si has valvet morphology.From the shape of hills on the surface varying with the orientation of Si wafer,we can conclude that chemical etching (CE) is preferential.Colour cycles appear in the etching process and while the colour cycles are at the critical time,the sample has the bnightest photoluminescence (PL).PL spectra show that the luminescent intensity of CE is nearly an order of magnitude smaller than that of PS formed by anodization.The peak energy of CE Si is from 1.94~2.04 eV,and the full width at half maximum intensity (FWHM) is from 0.25~0.41 eV.The Stability of CE Si is discussed,as well as that of PS formed by anodization.

Key words: silicon, chemical etching, photoluminescence