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 Eg, the spread in the tail of the band edge (parameter E0), the electrical resistivity ρ, 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 × 106 Ω cm and the appearance of a photoinjection current. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)