RAMAN-SCATTERING AND PHOTOLUMINESCENCE STUDY OF POROUS SILICON FORMED ON N-TYPE SILICON

We report Raman scattering and photoluminescence studies on porous silicon film formed on n-type silicon. The Raman spectra over the sample surface exhibit considerable variation whereas the photoluminescence spectra are practically identical. Our results indicate that, well inside the film surface, it consists of spherical nanocrystals of typical diameter approximate to 100 Angstrom, while on the edge these nanocrystals are greater than or equal to 300 Angstrom. We further observe that there is no correlation between the photoluminescence peak position and the nanocrystal diameter. This suggests that the origin of the photoluminescence is due to radiative recombination between defect states in the bulk as well as on the surface of the nanocrystal.