Study of nature of lattice vibration variations depending on a spatial distribution of zinc over the depth of Cd x Hg 1-x Te epitaxial layers grown on Cd 1-y Zn y Te substrates

Abstract

In this paper we report on the results of the study of optical properties of Cd_xHg_1-xTe epitaxial layers (EL) grown by the LPE method on Cd_1-xZn_yTe substrates. The values of the band gap of the solid solution forming EL have been obtained from the optical absorption spectra (FTIR) taken in the spectral region of the interband absorption at step-by-step decrease of EL thickness as a result of a chemical etching. In bridge with it the distribution and character of variations in the intensity of lattice vibrations over the layer depth of Cd_xHg_1-xTe / CdZnTe epitaxial structures was investigated. Longitudinal and transverse lattice vibration frequencies of Cd_xHg_1-x-yZn_yTe have been evaluated from the experimental spectra and compared with the theoretically calculated ones within a unit cell version of the random element isodisplacement model. From the comparing ofthe experimental and theoretical results it is possible to draw a conclusion that in immediate neighborhood of the Cd_xHg_1-xTe/Cd_1-yZn_yTe interface the Cd_xHg_1-x-yZn_yTe thin layer is formed under the certain conditions during the EL growth process i.e., zinc atoms in given EL area is necessary to consider not as an impurity atoms but as the components of the cationic sublattice.