Optical Characteristics of CdTe Films Deposited on Different Substrates by Thermal Evaporation Method in a Quasi-Closed Volume

Abstract

In the spectral range of 0.6—6.0 eV at 300 K, the transmittance and reflectivity, as well as photoluminescence in the range of 0.8—1.7 eV at 300 and 77 K, of thin films of cadmium telluride synthesized on different substrates by thermal evaporation in a quasi-closed volume were studied. A strong dependence of the intensity and position of the band-band and excitonic luminescence bands on the quality of the substrate was discovered. The excitonic luminescence bands of films on silicon and glass are shifted by 10 meV to the short-wavelength region due to the presence of internal stresses in the films owing to the mismatch between the parameters of the elementary cells of the substrate and the film. The transparency region of films cleaved from glass shifts to the long-wavelength region due to the density tails of electronic states in the band gap caused by disordering of the films and the excess of the light wavelength over the roughness of the films on the growth and nucleation side. Based on the obtained dependences of the intensity and spectral position of the photoluminescence lines, the best structural perfection is characteristic of films on a cadmium-tellurium substrate.