All relevant physical properties of semiconductors show spatial fluctuations. It is possible to analyze this spatial variation statistically using variogam analysis. The present paper gives a first example for the application of this method, for the case of charge-carrier effective lifetime, which was measured with the microwave-detected photoconductivity (MDP) system. It can be shown that different types of spatial distribution of defects in wafers are well-characterized by different variograms. Furthermore, there exist different spatial correlation ranges and variances of charge-carrier effective lifetime in wafers from different height positions in a brick. (C) 2009 Elsevier B.V. All rights reserved.