Photoluminescence Decay and Hydrogen Desorption of n-Type Porous Silicon

The decay under illumination of the photoluminescence (PL) intensity of n-type porous silicon (PS) samples prepared by electrochemical etching has been investigated. We have found that the PL evolution with illumination time presents two different stages: an initial very fast decay which lasts300 s, followed by a second one, much slower, which extends for times longer than 10 4 s. This evolution suggests that two different mechanisms could be responsible for the PL intensity decay. Samples subjected to different illumination times were studied by Thermal Desorption Spectroscopy (TDS). The desorption rate of H2 and SiHx species was monitored during linear heating of the samples. A qualitative correlation between the decay of the PL intensity under illumination and the amount of H2 and SiHx species evolved from the illuminated samples has been observed. Experimental data suggest that H2 could be desorbed from the sample during the illumination time through a photoinduced H2 desorption process, inducing the decrease of the PL intensity.