Al-doped ZnO (AZO) films were prepared by an Ar:

gas radio frequency (RF) magnetron sputtering system with a AZO (

) ceramic target at the low temperature of

and annealed in hydrogen ambient at the temperature of

. To investigate the influence of the

flow ratio on the properties of the AZO films, the

flow ratio was changed from 0.5% to 2%. As a result, the AZO films, deposited with a 1%

addition, showed a resistivity of

. When the AZO films were annealed at

for 1 hour in a hydrogen atmosphere, the resistivity decreased from

to

. The lowest resistivity of

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

flow ratio of 1% at 940 nm for GaAs/GaAlAs LEDs.