Electronic structure, optical and photoelectrical properties of crystalline Si2Te3

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, Si 2 Te 3 is an indirect-gap semiconductor with the calculated band gap calc gi E = 2.05 eV, close to the experimentally measured opt g E = 2.13 eV. The absorption edge and photoconductivity spectra of Si 2 Te 3 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 σ 0 , associated with the constant of electron-phonon interaction, and the energy of effective phonons ħω ph , involved in formation of the absorption edge of crystalline Si 2 Te 3 , 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 Si 2 Te 3 crystals.

Anisotropic optical properties of single Si2Te3 nanoplates

“…n = 2 for direct band gap transitions and n = 1/2 for indirect band gap transitions. Previous work by Bletskan et al 22 indicated an indirect band gap value of 2.13 eV for crystalline Si 2 Te 3 at room temperature. Bhattarai et al 6 have also shown that the stress has a strong effect on the band gap energy as well as the nature of the transition (i.e., direct or indirect).…”