This standard describes a particular method for measuring carrier lifetime, namely, that of photoconductive decay. Lifetime (volume) is defined as: the average time interval between the generation and recombination of minority carriers in a homogeneous semiconductor. Numerous methods for measuring carrier lifetime have been described, but this present standard concerns itself with the technique which has gained most widespread use. Discussion of basic theory and reference to other techniques will be found in the review paper by Bemski. This standard concerns measurements on both germanium and silicon, and in particular, describes the analysis of nonexponential decays often found in the case of silicon measurements. The smallest lifetime measurable by this method is determined by the turnoff time of the light sources as described in Section 2.2.1. The maximum measurable lifetime is determined by the diffusion constant D and the sample dimensions. Detailed limits for both n- and p-type germanium and silicon are presented in Table I (see Appendix).