Application of free carrier absorption for far-infrared detection

Far-infrared (FIR) free-carrier absorption characteristics for epitaxially grown p-type Si and GaAs thin films over a range of carrier concentrations have been investigated, both experimentally and theoretically, and employed to analyze the experimental results of FIR detection. The free-hole absorp tion is found to be almost independent of the wavelength and a linear regre ssion relationship between the absorption coefficient and the carrier conce ntration has been obtained, which can be applied to well explain the behavi or of GaAs FIR detectors with different number of layers, different applied biases, as well as different layer concentrations.