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addition, as shown in the above analysis, some of the defect properties can be deduced from the dependence. Thus, the temperature dependence of the carrier lifetime should be measured for various samples, including poly-crystalline Si wafers and silicon-on-insulator (501) wafers. Conclusion We have measured the temperature dependence of the carrier recombination lifetime for n- and p-type Si wafers by the photoconductivity decay method in a temperature range between room temperature and about 90 K. The car-rier lifetime of as-polished wafers has a very weak temper-ature dependence, while the lifetime of the oxidized wafer decreases steeply with decreasing temperature. From the comparison with calculation results, we have concluded that the level of the dominant recombination center is shal