Dark conductivity of silicon wafers has been measured as a function of doping levels: sample's geometry. and under gamma irradiation conditions. It has been shown that measurements of samples conductivity under different operating conditions can be used as an efficient method for material quality evaluation. In addition, gamma irradiation gives future information on Si-wafer quality, where it can effectively influence the material properties. The induced change in conductivity is discussed following, the mathematical difference of conductivity modulation mode. Using this model conductivity measurements could be considered as a good and simple technique for determining the silicon quality and for further development in silicon processing. (C) 2004 Elsevier Ltd. All rights reserved.