Study of flash evaporated CuIn1 − xGaxTe2 (x = 0, 0.5 and 1) thin films

CuIn1 − xGaxTe2 thin films with x = 0, 0.5 and 1, have been prepared by flash evaporation technique. These semiconducting layers present a chalcopyrite structure. The optical measurements have been carried out in the wavelength range 200-3000 nm. The linear dependence of the lattice parameters as a function of Ga content obeying Vegard's law was observed. The films have high absorption coefficients (4 · 104 cm− 1) and optical band gaps ranging from 1.06 eV for CuInTe2 to 1.21 eV for CuGaTe2. The fundamental transition energies of the CuIn1 − xGaxTe2 thin films can be fitted by a parabolic equation namely Eg1(x) = 1.06 + 0.237x − 0.082x2. The second transition energies of the CuInTe2 and CuGaTe2 films were estimated to be: Eg2 = 1.21 eV and Eg2 = 1.39 eV respectively. This variation of the energy gap with x has allowed the achievement of absorber layers with large gaps.