DECAY DYNAMICS OF THE HOMOGENEOUSLY BROADENED PHOTOLUMINESCENCE FROM POROUS SILICON

Dynamic properties of visible photoluminescence (PL) from porous silicon (PS) has been studied for PS samples prepared such that the PL spectra exhibit no significant inhomogeneous broadening. Even though both the excitation-wavelength dependence of PL spectra and the emission-wavelength dependence of PL excitation spectra are completely suppressed, the PL decay curves are nonexponential and the decay times still strongly depend on the emission wavelength. This implies that any structural inhomogeneity, such as a fluctuation in the Si cystallite size, is not directly responsible for the characteristic decay features of this material. A model is presented in which localized electron-hole pairs with various localization energies and pair distances in Si nanocrystallites couple with lattice phonons, resulting in the mixing of respective emission spectra.