Effects of electric field on the photoluminescence (PL) and surface morphologies of porous silicon (PS) were investigated. The decrease of PL intensity in presence of externally applied lateral voltage is due to the tunneling of electrons from neighboring quantum well to the holes taking part in the radiative recombination and supports the assumption of quantum confinement of holes as the origin of PL. AFM images showed that the small hilloxes, which can act as quantum wells and confine carriers in them, are intertinked within a certain range of dimension (that of the isolated regions) and can form quantum wire. (C) 2003 Elsevier Science B.V. All rights reserved.