SPECTRAL AND SPATIAL-BEHAVIOR OF RAMAN-SCATTERING AND PHOTOLUMINESCENCE FROM POROUS SILICON

Depth profiles of Raman scattering and the photoluminescence (PL) properties of anodized porous Si have been studied by micro-measurement techniques. In Raman spectra a remarkable low-energy shift and broadening of the optical phonon line are observed as compared with the bulk Si phonon line basically owing to the phonon confinement. In the depth profiles the PL shows blueshift correlating with the low-energy shift of the Raman peak as the measured point approaches the surface. The redshift of the PL peak has been observed with the low-energy excitation in normal-incidence experiments. It is concluded that the structural depth inhomogeneity strongly affects the optical properties of porous Si.