Journal of Porous Materials 7, 103–106 (2000) c  2000 Kluwer Academic Publishers. Manufactured in The Netherlands. Conduction and Luminescent Properties of Wet Porous Silicon B. GELLOZ Division of Electronic and Information Engineering, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, Japan gelloz@cc.tuat.ac.jp A. BSIESY Laboratoire de Spectrom´ etrie Physique, Universit´ e Joseph Fourier de Grenoble1 and CNRS (UMR5588), P.O. Box 87, 38402 St. Martin d’H` eres Cedex, France N. KOSHIDA Division of Electronic and Information Engineering, Faculty of Technology, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184, Japan Abstract. Carrier transport and photoluminescence-quenching mechanisms in reverse-biased p-type porous silicon in contact with an aqueous electrolyte are investigated. Concerning transport mechanisms investigation, experiments are based on the study of the photo-induced current as a function of the porous layer thickness. The liquid-impregnated porous silicon skeleton is found under equipotential conditions. Transport of electrons (supplied by the substrate) in porous silicon is shown to be dominated by a diffusion process. Photoluminescence-quenching is investigated by using a reverse-biased p-type porous silicon illuminated at 365 and 809 nm simultaneoulsy. The first illumination generate photoluminescence and the second supplies carriers in the substrate. A progressive photoluminescence-quenching has been observed, under a constant applied voltage, by increasing progressively the electron concentration in the porous layer. This original experiment allows to reject the hypothesis of an electric- field-induced separation of carriers as the photoluminescence-quenching mechanism in wet porous silicon, while it strongly supports the mechanism based on Auger recombination. Keywords: porous silicon, photoluminescence, electroluminescence, quenching 1. Introduction High external quantum yield, low applied voltages and voltage-induced spectral shift of the porous silicon electroluminescence (EL) [1] are the main attractive features of the liquid junction. In contrast, the porous silicon-solid electrode [2–4] device suffers from very low EL efficiency, high resistivity and the absence of important electrically-induced spectral shifts. An- other interesting property of porous silicon is voltage- induced photo-luminescence (PL) quenching. This phenomenon has been observed on porous silicon diodes with both solid and liquid contacts. With solid contact, the voltage-induced porous silicon PL quench- ing has been attributed to an electric-field-induced se- paration of carriers [5]. Liquid contact voltage-induced PL quenching has only been observed on direct-biased lightly doped n-type porous silicon [6]. It presents some differences compared to the PL-quenching obtained on solid state devices. First, the voltage needed to quench the PL is only about 1 V compared to several tens of volts in the case of the solid state devices. Sec- ond, on solid state devices, only a very weak spec- tral shift can be recorded [5] whereas on the liquid