Uzhhorod National University, Faculty of Physics, 54, Voloshyna str., 88000 Uzhhorod, Ukraine E-mail: crystal_lab457@yahoo.com

Abstract. In the framework of the density functional theory (DFT) in the approximation of local density adjusted for the strong correlation (LDA+U method), calculated were the band structure, total and partial densities of electronic states, as well as the spatial distribution of the electron density. According to the results of the calculation, Si2Te3 is an indirect-gap semiconductor with the calculated band gap = 2.05 eV, close to the experimentally measured = 2.13 eV. The absorption edge and photoconductivity spectra of Si2Te3 crystal within the temperature range 80...293 K have been measured. It has been shown that the dependence of the absorption coefficient on the photon energy is described by the Urbach rule. The parameter σ0, associated with the constant of electron-phonon interaction, and the energy of effective phonons ħωph, involved in formation of the absorption edge of crystalline Si2Te3, were determined using the temperature dependence of the absorption edge slope. Deviation from the stoichiometric composition in the direction of excess tellurium significantly affects the spectral distribution of the photoconductivity of Si2Te3 crystals.

Keywords: silicon sesquitelluride, electronic structure, electron-phonon interaction, absorption edge, photoconductivity.

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