Kinetics of exciton photoluminescence in low-dimensional silicon structures

Time-resolved photoluminescence (PL) spectra have been measured at 90–300 K in the visible spectral range for porous nanocrystalline silicon films fabricated by laser deposition. The energy and time ranges in which the spectra were taken were 1.4–3.2 eV and 50 ns–10 µs, respectively. The correlation between PL characteristics (intensity, emission spectrum, relaxation times and their temperature dependence), structure, and dielectric properties (size and shape of Si nanocrystals, oxide phase of their coatings, porosity of films) has been studied. A model of photoluminescence is adopted, in which the absorption and emission of photons occur in quantum-size nanocrystals, and in which kinetically coupled subsystems of electron-hole pairs and excitons are involved in the radiative recombination. Possible mechanisms of the exciton Auger recombination in low-dimensional silicon structures are proposed.