Far-infrared free-hole absorption in epitaxial silicon films for homojunction detectors

We report on the investigation of free-carrier absorption characteristics for epitaxially grown p-type silicon thin films in the far-infrared region (50-200 mu m), where Si homojunction interfacial workfunction internal photoemission (HIWIP) detectors are employed. Five Si thin films were grown by molecular beam epitaxy on different silicon substrates over a range of carrier concentrations, and the experimental absorption data were compared with calculated results. The free-hole absorption is found to be almost independent of the measured wavelength. A linear regression relationship between the absorption coefficient and the carrier concentration, in agreement with theory, has been obtained and employed to calculate the photon absorption probability in HIWIP detectors. (C) 1997 American Institute of Physics.