Crystal growth and structural, electrical, and optical characterization ofCuIn3Te5 and CuGa3Te5 ordered vacancy compounds

X-ray powder diffraction studies of ordered vacancy compounds CuIn3Te5 and CuGa3Te5, prepared by the vertical Bridgman-Stockbarger technique, show tha t these materials exhibit a tetragonal chalcopyrite-related structure. The unit cell parameters a and c are, respectively, 6.1639(3) and 12.346(2) Ang strom for CuIn3Te5, and 5.9321(8) and 11.825(4) Angstrom for CuGa3Te5. From electrical resistivity characterization as a function of temperature a sha llow acceptor level, with an activation energy lower than 30 meV, is found in both these compounds. Their direct energy gaps at room temperature are 1 .013 and 1.092 eV for CuIn3Te5 and CuGa3Te5, respectively. (C) 2000 America n Institute of Physics. [S0021-8979(00)06009-6].