Effect of lithium impurity on the opto-electrical properties of zinc oxide films

Lithium-doped zinc oxide (ZnO) films were prepared on C-plane sapphire substrates by the e-beam deposition technique in vacuum. The dependences of the optical absorption edge characteristics, structural, and photoelectrical properties on Li content (from 0 to 10 at.%) were investigated. It is found that the variations of the energy bandgap E-g, the spread in the tail of the band edge (parameter E-0), the electrical resistivity p, and the lattice constant c with impurity concentration do not have monotonic character. Abrupt jumps of the optical and electrical characteristics were observed as the impurity concentration changed near 0.8 at.% Li. The significant enhancement of photoconductivity response for 0.8 at.% Li-doped ZnO films also correlates with the enhanced electrical resistivity up to 2 x 106 Q cut and the appearance of a photoinjection current. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.