Abstract
The infrared plasma reflectivity and free carrier absorption of heavily Si‐doped n‐type 
are examined and the results show that shallow reflectivity minima 
and increased free carrier absorption cross sections are a consequence of high levels of compensation in the samples. The frequency dependence of the extinction coefficient 
in compensated as well as uncompensated samples is found to be different from that described by the Drude‐Zener theory in the frequency region near or higher than the plasma‐edge frequency. Based on the experimentally observed frequency dependence of 
, correction factors are evaluated in determining carrier concentration from the frequency of the infrared plasma reflectivity minimum when the reflectivity minimum is shallow. The correction factors are applied to the measured results of a series of samples and the resulting carrier concentrations are compared with those obtained from Hall effect measurements.