Radiative channel competition in silicon nanocrystallites

Photoluminescence and its temperature dependence, Raman scattering and photoluminescence excitation spectra for porous silicon, as well as their transformation during keeping in ambient air, have been investigated. The competition of different radiative channels was observed. It is shown that only one of them, that causes infrared emission band and dominates in as-prepared samples, is connected with excitonic recombination in Si nanocrystals. It is found that aging leads to an appearance of second radiative channel that causes red emission. Peculiarities of photoluminescence excitation and Raman scattering spectra, as well as of thermal quenching processes in porous silicon and the conditions for two radiative channel competitions are discussed.