Infrared absorption spectra in bulk Fe-doped InP

Abstract
We have observed that the absorption spectra in bulk Fe-doped indium phosphide differ considerably from those recorded on undoped and n-type samples. In the former case it was seen that the absorption edge presents a tail whose shape depends on the concentration of iron atoms incorporated into the matrix. Based on this phenomenon, we present a new nondestructive method which can be successfully employed to measure the iron concentration in semi-insulating InP.