A INTRODUCTION

The interest in the electrical properties of porous Si began prior to the discovery of its efficient luminescence [1 6]. The material was used for electrical isolation [1] and sensing [3, 7, 8] applications. Since Canham's report on porous Si luminescence, interest has shifted more towards the optical properties. Less effort has been devoted to the study of the transport, even though its understanding is essential for the design of optoelectronic devices. One reason for this is that light emission is rather localised in space (geminate recombination), while the transport involves motion of carriers over macroscopic distances, which is more difficult to address. Nevertheless, in recent years the number of reports on transport in porous Si has increased rapidly and a better understanding of the phenomena controlling conduction processes has been achieved.

From early studies of the conduction in porous Si it became clear that the material has a rather high resistivity [2, 5, 7]. The resistivity is very sensitive to the ambient atmosphere [3, 8]. Therefore, one cannot cite a unique value for the resistivity of porous Si. Instead, in this Datareview, we will give a description of the parameters influencing electrical conduction in porous Si and describe the various mechanisms suggested for transport.

The usual division between macro, meso, and microporous Si is according to pore size. This is of little use for transport, since current flows through the Si network. Here, the relevant parameter is the typical...