Infrared absorption of laser deposited PbSe films

Abstract

The transmission spectra of later-deposited PbSe films have been measured over the wavelength range 2-5 mu m at different temperatures over the range 90-310 K. The dispersion of the refractive index and the spectral dependence of the absorption coefficient for samples with various carrier concentrations have been obtained. The values of the optical dielectric constant epsilon infinity , the susceptibility effective mass msigma and the energy gap at different temperatures have been determined. From the concentration dependence of msigma at the Fermi level, the values of the longitudinal and transverse effective masses at the top of the valence band have been found. The authors' interpretation of the spectral dependence of the absorption coefficient leads them to the conclusion that an absorption additional to free-carrier and interband absorption takes place in the samples. In their view this additional absorption can be attributed to a defect resonant level in the valence band.