Reflectance measurements from p-type GaSb: Zn epitaxial films with different hole concentrations(1017-1018 cm−3) have been investigated over the frequency region of 100-1000 cm−1. A minimum broadening feature corresponding to the hole plasmon was observed in the reflectance spectra. The experimental infrared spectra were well fitted using a Lorentz-Drude dispersion model. The real part ε1 of the dielectric function decreases with increasing hole concentration. However, the imaginary part ε2 increases with hole concentration in the far-infrared region. This indicates that the acoustic- and optic-phonons mainly participate in the free carrier absorption processes. The hole mobility obtained from Hall-effect measurements is slightly larger than that derived from optical measurements and the average ratio of mobilities is estimated to be 1.33. Owing to overdamping effects, the upper branch of longitudinal-optical phonon plasmon (LPP) coupled modes was observed. The upper LPP+ frequency increases with hole concentration and it shows a transition from phonon-like to plasmon-like behavior. A theoretical analysis with solutions in the complex frequency plane describes these experimental results.

The optical properties of hexagonal AlxGa1−xN x from 0.05 to 0.42 epitaxial films with Sim doping concentrations up to 1018 cm−3 grown on c-plane sapphire substrates by metal-organic chemical vapor deposition have been investigated using infrared reflectance spectra. The dielectric functions=1+i2 of the AlxGa1−xN films are determined in the wavelength region of 1.54-50m at room temperature. The experimental reflectance spectra are analyzed using classical harmonic Lorentz oscillators and Drude model in the transparent,reststrahlen, and free carrier absorption regions. GaN-like E1 transverse-optical TO phonon frequency linearly decreases and its strength increases with decreasing Al composition. However, AlN-like E1 TO phonon frequency shows a relatively weak composition dependence and its strength increases with increasing composition. At a wavelength of 1.54m, 1 varies between 4.86 and 5.2 when the composition changes from 0.05 to 0.42 and 2 is close to zero. The longitudinal-optical phonon plasmon LPP coupled modes of n-type hexagonal AlxGa1−xN films are also discussed. For samples with higher concentrations beyond 1018cm−3 the upper LPP coupled mode frequencies increase with increasing carrier concentration indicating the transition from phononlike to plasmonlike behavior.

Lead lanthanum zirconate titanate (PLZT) thin films with different La concentrations (x), whose composition is x/40/60, have been grown directly on Pt/Ti/SiO2/Si (100) substrates by a modified sol-gel method. X-ray diffraction analysis shows that the PLZT thin films are polycrystalline. The infrared optical properties of the PLZT thin films have been investigated using the infrared spectroscopic ellipsometry in the spectral range of 2.5–12.5 μm. By fitting the measured ellipsometric spectra (Ψ andΔ) with a three-phase model (air/PLZT/Pt), and a derived classical dispersion relation for the thin films, the optical constants and thicknesses of the thin films have been obtained. The refractive index of the PLZT thin films decreases with increasing La concentrations, however, the extinction coefficient increases with increasing La concentrations except for the PLZT(4/40/60) thin films. The values of the effective static charge calculated for the PLZT thin films, which state that PLZT belongs to a mixed ionic-covalent compound, decrease with increasing La concentrations. Moreover, the refractive index at the wavelength of 2.5 μm changes linearly with the effective static charge. The plot of the calculated infrared optical absorption versus wavelength for the Ni/PLZT/Pt multilayer structures with various La concentrations is given and indicates that the PLZT thin films are excellent candidates for ferroelectric infrared detectors and focal plane arrays.

Optical properties of ferroelectric Bi3.25La0.75Ti3O12 BLT films on quartz have been investigated using ultraviolet-infrared transmittance spectra in the temperature range of 77-500 K. The spectra can be divided into three distinctive photon regions between 1.1 and 6.5V. It is found that the band gap Eg decreases from 3.88 to 3.77V with the temperature. The parameters aB and B of the Bose-Einstein model are 30.3V and 218.7K, respectively. The band narrowing coefficient dEg/dT is −2.65 10−4V/K at room temperature. The present results can be crucial for future application of ferroelectric BLT-based electro-optic and high temperature optoelectronic devices.

Optical anisotropy of hexagonal Ga1−xMnxN(x from 0.0% to 1.5%) epitaxial films grown on c-plane sapphire substrates has been investigated using far- and mid-infrared s- and p-polarized reflectance spectra at oblique incidence at 10, 22, and 32, respectively. The experimental data at room temperature can be well reproduced simultaneously in the measured frequency region of 200-2000 cm−15-50 m, which was based on a four-phase layered system using a 4×4 matrix method M. Schubert, Phys. Rev. B53, 4265(1996). The lattice vibrations perpendicular and parallel to the optic c axis(E1 and A1 modes) were expressed by Lorentz oscillator dielectric function model. There was a striking absorption dip at the A1 phonon frequency in p-polarized reflectance spectra due to the optical anisotropy. These infrared-active phonon parameters were obtained with uniaxial dielectric tensor. It was found that the A1 longitudinal-optical phonon frequency linearly increases with the Mn composition for the diluted magnetic semiconductor epilayers. The broadening values of the A1 phonon changed from 3.6±1.3 to 9.0±1.6 cm−1, showing the high film crystal quality. Moreover, the ordinary and extraordinary dielectric functions ε⊥ and ε‖ of the epilayers were determined. It indicated that was larger than ε⊥ for the Ga1−xMn x N films in the reststrahlen region, which can be ascribed to slight structural degradation of the wurtzite lattice.