Infrared absorption of n- and p-type Fe-doped InP and mapping of the Fe distribution

The near-IR absorption spectra of n- and p-type Fe-doped InP were measured at room temperature in a wide range of Fe concentrations. A clear correlation was found between the Fe content in the InP samples which were only Fe-doped and the optical IR absorption. The absorption coefficient at 1000 nm depends linearly on the chemical Fe concentration. The same dependence was observed for Te/Fe (n-type) as well as for Zn/Fe (p-type) co-doped InP. This effect is used for a quantitative evaluation of the Fe distribution across whole wafers (mapping). The results are compared to those of other characterization techniques, e.g. selective etching, showing an excellent agreement.