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

Abstract

The transmittance, reflectivity, and photoluminescence in the range 0.8–1.7 eV at 300 K and 77 K in the spectral range 0.6–6.0 eV at 300 K of thin films of CdTe 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 substrate quality was discovered. The excitonic luminescence bands of films on silicon and glass were shifted by 10 meV to the short-wavelength region because of internal stresses in the films owing to the mismatch between the unit-cell parameters of the substrate and film. The transparency region of films cleaved from glass shifted to the longwavelength region because of the density tails of electronic states in the band gap caused by disordering of the films and the longer wavelength of the light than the roughness of the films on the growth and nucleation side. The best structural perfection was characteristic of films on a CdTe substrate based on the obtained dependences of the intensity and spectral position of the photoluminescence lines.