Optical properties of CdSexTe1−x epitaxial films studied by spectroscopic ellipsometry

Abstract

We have determined the dielectric constants for a series of CdSe x Te 1-x thin films grown on Si substrates using a rotating-analyzer spectroscopic ellipsometer. Initially, the alloy concentration and the sample quality were determined using x-ray diffraction. A standard inversion technique was then used to obtain the dielectric constants from the measured ellipsometric spectra. Using these calculated absorption spectra, we were able to estimate the fundamental bandgap for these CdSe x Te 1-x alloys. In addition, we also determined the dispersion of the indices of refraction as well as the critical points related to the higher-order electronic transitions for this alloy.

Ellipsometric Analysis of Cadmium Telluride Films’ Structure

“…There are papers where properties of a cadmium telluride films are studied using the ellipsometric method. In [1][2][3][4][5][6][7] and also in our papers [8,9], it is shown that the surface structure and film optical constant values strongly depend on the methods and conditions of film deposition. Specifically, film optical constants, refractive index and index of extinction , appeared to differ perceptibly from optical parameters of monocrystalline cadmium telluride.…”

Exploring the Optical Properties of Hg1−x Cd x Se Films Using IR-Spectroscopic Ellipsometry

“…If a sample is made of several layers, both the dielectric function (e = e 1 + ie 2 ) and the thickness of each layer affect W and D. Since ellipsometry is an inverse problem, a model is established to represent the sample structure, which consists of a sequence of layers with abrupt interfaces, bound by a semi-infinite substrate and the ambient. 12 Varying the model parameters, a regression analysis is subsequently performed, until the calculated and experimental data match with each other. This analysis finally results in determining the e of the unknown film which is of great significance.…”

“…The disappearance of the oscillations in both spectra above a specific energy ($0.3 eV) signals the transition to the absorption region. 12 In order to obtain the thickness and the dielectric function, the ellipsometry data were fitted using a three-layer model (GaSb substrate, Hg 1Àx Cd x Se film, and a surface-oxide layer). As the optical properties of the substrate are known, the thicknesses of the other two layers and the optical properties of Hg 1Àx Cd x Se layer were adjusted to match the experimental data.…”