EFFECTS OF Al, Ga-DOPING ON TRANSPARENT CONDUCTING PROPERTIES OF AMORPHOUS ZnO-SnO₂ FILMS

ZnO SnO 2 thin films were deposited on glass substrates (Corning#1737) by DC magnetron sputtering. In this works, we examined a doping effect on a ZnO target on transparent conducting properties. ZnO:Al (4wt%), and ZnO:Ga (6wt%) targets were used for a dopant-free ZnO target. Substrate temperature was held at 250°C. The current ratio δ was defined as IZn/IZ + ISn ( ZnO target current divided by the sum of ZnO and SnO 2 target currents). Compositions of as-deposited films were changed with the current ratio δ. In the ZnO-SnO 2 system, amorphous transparent films appeared over the range of 0.33≤δ≤0.73. On the other hand, in the ZnO:Al (4 wt %)- SnO 2 and ZnO:Ga (6 wt %)- SnO 2 systems, they appeared over the range of 0.20≤δ≤0.80 and 0.33≤δ≤0.80, ≤δ≤ respectively. The minimum resistivity of amorphous films was about 3.0×10-2 Ω cm for all the systems. Al , Ga doping effect on film resistivity was not clear very much. But optical transparencies were 80-90% in visible region, 10% higher than those of ZnO-SnO 2 system at average. Optical band gap for the films with the same current ratio δ also was enhanced by the Al , Ga doping.