Positional variation and annealing effect in magnetron sputtered Ga-doped ZnO films

• As-deposited films show an exponential-like resistivity change with c-axis length.
• Thermal annealing changes electrical and structural properties.
• Three different types of defect exist in the as-deposited films.

Positional distribution of electrical resistivity and crystalline lattice constant of Ga-doped ZnO films deposited by the magnetron spattering method at room temperature have been investigated. Electrical resistivity and c-axis lattice constant strongly depended on substrate position and substrate–target distance when the films were deposited without substrate heating. Films deposited at the positions facing erosion region showed higher electrical resistivity, less carrier density and elongated c-axis lattice constant than those deposited at the other positions. These films showed exponential-like change of resistivity and carrier density as a function of c-axis lattice constant in a wide range of substrate–target distance. Thermal annealing decreased resistivity and c-axis lattice constant of the as-deposited films and homogenized the positional distribution of their properties. Comparison of electrical and structural changes between before and after the annealing revealed that there are at least three types of defect in the sputtered Ga-doped ZnO films that affect carrier density and mobility with different annealing behaviors.