Contaminants in a semiconductor reduce the lifetime.  By far, the most common heavy metal contaminant is iron, as it is part of stainless steel and finds its way into equipment and liquids.  In most semiconductor materials and processes, there are tight specs on the amount of allowable iron, as iron contamination leads to junction leakage, breakdown problems, and reliability problems.  Although iron contamination can be detected by a lifetime or diffusion length measurement, it is often desirable to determine that the degradation in lifetime or diffusion length was caused by iron and to determine the amount of iron contamination present in the sample. This information, particularly if shown in a map, speeds troubleshooting. In p-type wafers it is relatively easy to identify and quantify iron contamination. The technique works with either µ-PCD or SPV. Technical note #205 explains the theory in detail.