STUDY OF CUGA(SE, TE)2 BULK MATERIALS AND THIN-FILMS

We have grown and studied CuGa(Se,Te)2 photovoltaic bulk materials and thin films. This compound can readily be grown with p-type conductivity and can have a very good lattice match with CdS for a Se:Te ratio giving an energy pp close to 1.5 eV. The lattice parameters were determined by x-ray diffraction, and the energy gap calculated for temperatures between 77 and 300 K from luminescence studies. Thin films were grown using a close-spaced vapor transport technique, with iodine as reagent. The chemical equations governing the transport were determined. Good-quality CuGaSe2 thin films were easily grown, but we could not get CuGa(SexTe1-x)2 thin films when x < 0. 5. This result was explained from the CuGaTe2 phase diagram. Thermal evaporation experiments gave us similar results, but flash evaporation gave us thin films with a composition close to the source composition.