Transparent ZnO:Al2O3 films with high breakdown voltage and resistivity.

Transparent ZnO films with high breakdown voltage and resistivity were deposited by the radio frequency-assisted evaporation method. In this paper, we have investigated on the structural, optical, and electrical properties of ZnO:Al2O3. The preferred orientation of the columnar structured in situ-grown film was along (002). The resistivity of the films was five orders of magnitude larger than the current's highest resistivity. The breakdown voltage of the film (8571 V/mm) was five times higher than the highest reported breakdown voltage for a ZnO semiconductor. Furthermore, the ZnO:Al2O3 film was transparent in the visible and infrared regions even though the film had an Al content of about 7% and a thickness of 100 nm. The high-frequency dielectric constant of the ZnO:Al2O3 film was higher than that of Al2O3. The possible reasons for the transparent ZnO:Al2O3 film behavior were second-phase Al2O3, lower carrier concentration, and strong bound electrons. Less defects and strong bonding contribute 4 orders of magnitude improvement to the high resistivity of ZnO films. The obtained results suggest that ZnO:Al2O3 can be used as an insulator layer between the p-n junction in order to improve the efficiency of the solar cell device. [ABSTRACT FROM AUTHOR]