In this work, we present the measurements of reflectance, luminescence and photocarriers lifetime for monocrystalline Si substrates covered with a polycrystalline undoped Si1-xGex thin film made porous by stain etching. The reflectance of the samples decreases from similar to39 to similar to8% when the Si1-xGex thin film is made porous. The porous films are photoluminescent, showing a slight redshift when the Ge amount of the film increases. Nevertheless, the growth of the Si1-xGex thin film diminishes the lifetime values, which does not vary after the Si1-xGex surface is passivated with a SiNx thin film. However, when the Si1-xGex. thin film is made porous, a slight increase of the lifetime is observed. These results are discussed in terms of application of these thin films in solar cells and photodetectors. (C) 2003 Elsevier B.V. All rights reserved.