Possibilities of characterizing the crystal parameters of Cd$_{x}$Hg$_{1-x}$Te structures on GaAs substrates by the method of generation of the probe-radiation second harmonic in reflection geometry

Results of numerical simulation and experimental data on recording azimuthal angular dependences of a second-harmonic signal reflected from Cd$_{x}$Hg$_{1-x}$Te structures and GaAs substrates at normal incidence of probe laser radiation on the sample and azimuthal rotation of its polarization plane have been compared. It is found proceeding from the results of studying (013)GaAs substrates and CdTe|ZnTe|GaAs buffer layers that deviations from the (013) surface orientation were 1$^\circ$–3$^\circ$ (in crystallophysical angles $\Theta$ and $\varphi$ for GaAs substrates and up to 8$\circ$ for CdTe|ZnTe|GaAs buffer layers; the magnitude of the second-harmonic signal from the buffer layers can be assumed inversely proportional to the FWHM of X-ray rocking curves. It is shown based on the experimental data that components of the nonlinear susceptibility tensor $\chi_{xyz}(\omega)$ of the Cd$_{x}$Hg$_{1-x}$Te crystal structure are much larger than those for CdTe and GaAs.