Formation of a porous structure on the surface of Ge single crystals by pulsed YAG:Nd laser irradiation at the intensity of similar to 25 MW/cm(2) is reported. An increase of surface recombination velocity on the irradiated surface by a factor of 100 is observed and explained by increase of the geometric area of the surface due to formation of pores. The latter is attributed to inhomogeneous pressure of a pulsed laser beam on the melting irradiated surface of the crystal. (c) 2004 Elsevier B.V. All rights reserved.