Degradation effect of porous silicon on photoacoustic and photoluminescence signal intensities with photoexcitation

Abstract

The discovery of efficient photoluminescence (PL) from electrochemically anodized porous silicon (PS) initiated a strong effort to characterize and understand PS properties. It was noted that quite soon after the discovery, PL undergoes significant degradation (long term instability) under normal photoexcitation conditions. Determining the source of the degradation is not only important with regard to assessing the optoelectronic potential of luminescent PS, but also might provide further insight into the origin of the luminescence and factors that control efficiency. In this article, we report the time-dependence of the photoacoustic (PA) signal intensities of PS with different anodization and etching times together with that of PL signal intensities. PA method is a photothermal (PT) technique, which is useful to obtain optical absorption characteristics for strongly scattering PS and existence of a silicon substrate. The experimental results suggest that the changes of the optical absorption centered by light exposure is different from that of luminescent center in anodizing and etching conditions, indicating the difference of photoenhanced oxidization processes (photochemical, photothermal, photoelectric and photostructure) in these conditions.