Investigations on polycrystalline CuGaTe2 thin films

Polycrystalline and single-phase CuGaTe2 thin films (0.4-1.0 mu m thickness) were prepared by flash evaporation of the pre-reacted material, synthesized from its constituent elements. The films were deposited on glass substrates at temperatures in the range 303-623 K. The physical behaviour of the films was found to be highly influenced by the substrate temperature, T-s. The films formed at T-s = 523-573 K were nearly stoichiometric and exhibited (112) preferred orientation with tetragonal structure. The evaluated lattice parameters were a = 6.025 Angstrom and c = 11.996 Angstrom. The electrical conductivity of the films varied in the range 10-10(2) Ohm cm. Two activation energies corresponding to shallow and deep acceptor levels were observed. The films showed a three-fold optical structure with the bandgaps at 1.23 eV, 1.28 eV and 1.98 eV. The optical constants, dielectric constant, plasma frequency and the effective mass of the charge carriers were computed. The results are discussed to study the suitability of CuGaTe, films for solar cell application.