New buffer layers, large band gap ternary compounds: CuAlTe2

After deposition, by evaporation under vacuum, of Al/Cu/Te. multilayer stru ctures, annealing at 673 K or more for half an hour, under argon flow, allo ws CuAlTe2 films crystallised in the chalcopyrite structure to be obtained. The optical and electrical properties are interpreted by introducing the i nfluence of impurity foreign phases present in the films. The optical prope rties are sensitive to the small Al2O3 domains randomly distributed into th e CuAlTe2 polycrystalline matrix. The optical band gap is slightly increase d (2.35 eV) by the presence of alumina. The conductivity measurements show that a short circuit effect can be induced by a binary Cu2-xTe degenerate p hase present at the surface of the films. This effect can be suppressed by KCN etching of the samples that allows the superficial foreign phase to be dissolved.