EXCITATION AND RECOMBINATION PROCESS IN POROUS SILICON

Light excitation spectrum of visible luminescence of porous Si and the temperature dependence of the luminescence spectrum have been studied. The band gap of the luminescent Si nanostructure in the porous Si is found to be about 2 eV from the analysis of the excitation spectrum. The visible luminescence is inferred to be due to the recombination of localized excitons with strong phonon coupling. This shows that an electron-hole pair created by the band-to-band excitation in a luminescent Si nanostructure is trapped at a luminescence center and forms a localized exciton which results in the visible light emission.