Damp Heat Durability of Al-Doped ZnO Transparent Electrodes with Different Crystal Growth Orientations

Abstract

Al-doped ZnO (AZO) transparent electrodes deposited by reactive sputtering are investigated to clarify the influences of crystal orientations on film durability. During the deposition, argon gas flow was varied from 3 to 60 sccm amidst fixed oxygen gas flow at 60 sccm. With increasing argon gas flow, the crystal orientations exhibit a major transition from (110) to (002). During damp heat test at 85% relative humidity and 85°C, the films with more variations in crystal orientations exhibit more decreased Hall mobility, while the films having crystal orientation (002) exhibit less reduced carrier concentrations. Conductivity degradation over time is monotonous with argon gas flow, and the tendency is more similar to reduced carrier concentrations rather than decreased mobility. It is suggested that the degradation differences among AZO films are rather caused by the effectiveness of major crystal orientation in protecting carrier concentrations.