Photoluminescence decay in porous silicon films

The photoluminescence (PL) decay measurements were performed on porous silicon films. It was observed that the two components of PL, one of them fast (ns) and the other slow (microsecond(s) or ms sometimes) have different contributions to PL signal, depending on the wavelength of the excitation light. The slow component of PL was in details investigated. Time decay cures for different excitation (337.1 nm, 470 nm, and 550 nm) and emission (550, 650, 700, 800 and 860 nm) wavelengths and also for different excitation intensities were taken. All decay curves were fitted with a stretched exponential. The slow component of PL was proposed to be attributed to the radiative recombination on surfaces.