Correlation of Photoluminescence and Optical Absorption Spectra of Porous Silicon

Using a quantum confinement based-PL model, PS was modelled as a mixture of Quantum Dots (QDs) and Quantum Wires (QWs) having different concentrations and sizes. It was shown that in the optical absorption edge the PL peak energy and the Optical Absorption (OA) exhibit the same trend, depending on preparation conditions. The spectral behaviours of PL and OA are analysed and correlated throughout the shapes and the size distribution of the nanocrystallites forming PS. Using the quantum confinement formalism, the value of the effective band-gap energy determined from the lowest PL energy almost corresponds to that estimated from the optical absorption coefficient. These results suggest that the lowest radiative transition between the valence band and the conduction band corresponds to the largest luminescent wires, and that the radiative recombination process leading to the PL emission occurs in the c-Si crystallite core.