Physical and optical properties of polycrystalline Cu$_{0.27}$Ga$_{1.85}$Se$_{1.88}$ and Cu$_{0.33}$Ga$_{1.54}$Se$_{2.13}$, films synthesized by controlled selenization

Polycrystalline films of Cu$_{0.27}$Ga$_{1.85}$Se$_{1.88}$ and Cu$_{0.33}$Ga$_{1.54}$Se$_{2.13}$ with a chalcopyrite structure of the Cu–Ga–Se system were synthesized. The effect of selenization temperature on the chemical composition and structure of films was studied by X-ray phase analysis and electron microscopy. The dependence of film resistance on concentration and temperature has been studied. The effect of photoconductivity was discovered on Cu$_{0.27}$Ga$_{1.85}$Se$_{1.88}$ films. The Raman spectra of these films were calculated. From the absorption spectra, the Urbach energy $E_{\mathrm{U}}$ = 0.9 eV was determined, which indicates a nouniform distribution of localized states in the electronic structure of the films. Migration and dipole-orientation contributions to the electrical polarization of the films have been established. Using the Debye model, the relaxation time in film samples of the Cu–Ga–Se system was calculated.