Minority carrier lifetime and iron concentration measurements on p -Si wafers by infrared photothermal radiometry and microwave photoconductance decay

A comparative study of electronic transport properties of p-Si wafers intentionally contaminated with Fe was performed using infrared photothermal radiometry (PTR) and microwave photoconductance decay (μ-PCD). Strong correlations were found between PTR and μ-PCD lifetimes in a lightly contaminated wafer with no significant PTR transient behavior. The absolute PTR lifetime values were larger than the local averaged μ-PCD values, due to the different excitation wavelengths and probe depths. In a heavily contaminated wafer the μ-PCD and PTR lifetime correlation was poorer. PTR measurements were highly sensitive to iron concentration, most likely due to the dependence of the bulk recombination lifetime on it. Rapid-scanned (nonsteady-state) PTR images of the wafer surface exhibited strong correlations with both μ-PCD lifetime and [Fe] concentration images in both heavily and lightly contaminated wafers. For the lightly and uniformly contaminated wafer, PTR scanning imaging was found to be more sensitive to iron concentration and lifetime variations than μ-PCD images.