Infrared Dielectric Constant and Ultraviolet Optical Properties of Solids with Diamond, Zinc Blende, Wurtzite, and Rocksalt Structure

Abstract

The room-temperature optical constants of InP, CdTe, and ZnTe are calculated for photon energies up to 20 eV by the Kramers-Kronig analysis of the normal-incidence reflection spectra. Data at 77°K are also presented for ZnTe and CdTe. At these temperatures, asymmetries in some of the peaks in ε2, of the type attributed by Phillips to resonant exciton effects interacting with a continuous background, are seen. The position of the E2 peaks (due to transitions at X) is listed for materials of the diamond-zinc blende family, as observed in the spectrum of R (the reflection coefficient), ε1, ε2 (real and imaginary parts of the dielectric constant) n, k (real and imaginary parts of the refractive index), and the absorption coefficient α. We have also listed the various peaks corresponding to E2 peaks of zinc blende for materials with wurtzite structure. The infrared dielectric constant ε∞ is calculated for these materials from the position of E2 on the base of Penn's model for an isotropic free electron gas with an energy gap. Good agreement with the experimental values of ε∞ is obtained. The model is generalized to treat PbS, PbSe, PbTe, and SnTe. Good agreement between calculated and experimental values of ε∞ is also obtained for these materials.