Optical properties of porous silicon

The optical properties of porous silicon are discussed in a wide spectral range from the infrared to the ultraviolet. The analysis is done by a simulation method which adjusts parameters of dielectric function models to fit experimentally obtained reflectance spectra. Charge carriers and vibrational modes of surface-covering atoms like hydrogen and oxygen determine the infrared spectra whereas interband transitions are observed in the visible and ultraviolet range. The obtained optical constants are compared to theoretical band structure computations for ''quantum wires'' and ''quantum spheres''. A study of aging effects and the discussion of ''porosity superlattices'' as optical filters are pointing to the application of porous silicon layer systems in optical devices. In addition, external efficiencies of photo-and electroluminescence experiments are given on the basis of the determined optical properties of porous silicon.