https://doi.org/10.15407/jopt.2018.53.273

Optoelectron. Semicond. Tech. 53, 273-281 (2018)

I. E. Matyash, I. A. Minaіlova, O. N. Mishchuk, B. K. Serdega

COMPONENT ANALYSIS OF PHONON SPECTRA DYCHROIDISM IN UNIAXIALLY DEFORMED SILICON CRYSTAL

The effect of linear dichroism induced by uniaxial compression has been researched in semiconductor silicon by using the method for polarization modulation of electromagnetic radiation. The use of the modulation polarimetry technique provides detectivity relative to the magnitude of anisotropy Δn/n≈10-6. This fact allows us to register insignificant deviations of physical parameters from equilibrium. The spectral characteristics of the polarization difference of the transmission coefficients ΔТ = Т⊥ – Т|| were obtained within the range of light absorption near the fundamental edge. The characteristic ΔТ(ω) is a derivative of the transmission spectrum, from which the spectrum of the absorption coefficient of radiation based on the Bouguer-Lambert law is determined. There are no errors in the characteristic obtained by the method of modulation polarimetry, in contrast to the mathematical differentiation of experimental results. The characteristics of the physical derivative demonstrate a fine structure with attributes of various spectral components due to this advantage. Decomposition of the spectra into Gaussian components was performed on the basis of these features, and the types of phonons as well as their frequencies were determined. One of them is related to the sample thickness by the spectrum shift, while the other three extremes are fixed relatively to the energy of the forbidden band. The conclusion about the origin of detected components of dichroism, being based on the references and fact of a lightly doped crystal has been made. The presence of dichroism components is caused by the manifestation of acoustic phonons participating in indirect interband transitions with quantum energies both lower and higher than the energy of the forbidden band. The paper shows that the effect of linear dichroism in combination with the modulation polarimetry method can be a good diagnostic technique for semiconductor crystals and devices. This will allow one to test the features of the band spectrum, the presence of inhomogeneities of crystals and related internal mechanical stresses.

Keywords: polarization, anisotropy, dichroism, modulation polarimetry, silicon, phonon, Gaussian function.