STRUCTURAL, ELECTRICAL AND OPTICAL-PROPERTIES OF CUGA0.75IN0.25SE2 THIN-FILMS

CuGa0.75In0.25Se2 thin films (0.1-2.0-mu-m) grown on Corning 7059 glass substrates at T(s) = 598-648 K were nearly stoichiometric, single phase, polycrystalline and exhibited electrical resistivity in the range 30-300-OMEGA cm. Thermoelectric power and Hall effect measurements indicated p-type conduction in the films. The temperature dependence of the electrical conductivity suggested that above 460 K the conduction mechanism was intrinsic, whereas extrinsic/impurity conduction dominated in the range 303-450 K. The optical absorption spectra of CuGa0.75In0.25Se2 thin films revealed absorption humps which were attributed to valence subbard transitions. The (alpha-h-nu)2 versus photon energy curves indicated a direct fundamental gap of 1.50 eV. Band splitting by crystal-field and spin-orbit effects were observed respectively at 1.57 and 1.75 eV.