The Electrical and Optical Properties of Al-Doped ZnO Films Sputtered in an Ar:H2Gas Radio Frequency Magnetron Sputtering System

Abstract

Al-doped ZnO (AZO) films were prepared by an Ar:<TEX>$H_2$</TEX> gas radio frequency (RF) magnetron sputtering system with a AZO (<TEX>$2\;wt{\cdot}%\;Al_2O_3$</TEX>) ceramic target at the low temperature of <TEX>$100^{\circ}C$</TEX> and annealed in hydrogen ambient at the temperature of <TEX>$300^{\circ}C$</TEX>. To investigate the influence of the <TEX>$H_2$</TEX> flow ratio on the properties of the AZO films, the <TEX>$H_2$</TEX> flow ratio was changed from 0.5% to 2%. As a result, the AZO films, deposited with a 1% <TEX>$H_2$</TEX> addition, showed a resistivity of <TEX>$11.7\;{\times}\;10^{-4}\;{\Omega}{\cdot}cm$</TEX>. When the AZO films were annealed at <TEX>$300^{\circ}C$</TEX> for 1 hour in a hydrogen atmosphere, the resistivity decreased from <TEX>$11.7\;{\times}\;10^{-4}\;{\Omega}{\cdot}cm$</TEX> to <TEX>$5.63\;{\times}\;10^{-4}\;{\Omega}{\cdot}cm$</TEX>. The lowest resistivity of <TEX>$5.63\;{\times}\;10^{-4}{\Omega}{\cdot}cm$</TEX> was obtained by adding 1% hydrogen gas to the deposition and annealing process. The X-ray diffraction patterns of all the films showed a preferable growth orientation in the (002) plane. The spectrophotometer measurements showed that the transmittance of 85% was obtained by the film deposited with the <TEX>$H_2$</TEX> flow ratio of 1% at 940 nm for GaAs/GaAlAs LEDs.