STRUCTURAL, ELECTRICAL, AND OPTICAL-PROPERTIES OF CUGASE2 RF-SPUTTERED THIN-FILMS

Thin films of CuGaSe2 have been produced by rf sputtering. Compositional, structural, electrical, and optical properties are strongly influenced by growth temperature. At substrate temperatures lower than 300°C amorphous or poorly crystalline Se-excess films are obtained, showing high resistivity (≊103 Ω cm) and optical transitions at 1.62, 1.80, and 2.4 eV (values lower than the single-crystal counterparts). At the higher growth temperatures, polycrystalline films are obtained (average grain size 0.7 μm) with lower values of resistivity (1 Ω cm), and optical transitions at 1.68, 1.90, and 2.55 eV (very close to the single-crystal values). A hopping conduction mechanism has been detected at the lower measuring temperature (T<150 K), and a grain boundary limited conduction process at the higher measurements temperature (T>150 K). Structural and compositional characteristics are used to explain the behavior observed in the electrical and optical properties.