Study of flash evaporated Culn1-x GaxTe2 (x=0, 0.5 and 1) thin films
Résumé
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.