Diode properties of structures containing a porous silicon layer have been investigated. The structures have been fabricated by depositing metal or indium‐tin‐oxide layers either directly on the ‘‘as‐anodized’’ silicon wafer or on the wafers with upper, nanocrystalline part of the porous layer removed. Different behavior was observed in both cases: (1) The photovoltaic effect is absent in diodes from as‐anodized wafers but appears in diodes from the cleaned wafers; (2) the diode ideality factor is close to 2 for ‘‘cleaned’’ diodes and increases in diodes containing an upper porous silicon layer. Energy‐band diagrams for the structures are proposed and it is concluded that the electrical transport in those structures is limited by the carrier recombination in the depletion layer. ©1995 American Institute of Physics.