A successful attempt was made to improve the carrier mobility in rf-sputtered ZnO:aAl films. The electrical and optical film properties were found to be mainly determined by Al doping concentration, film thickness, sputter pressure, and substrate temperature, while grown rate and sputter power showed a comparatively small influence. As such, secondary ion mass spectrometry (SIMS) results revealed that the Al incorporation into the film was linearly dependent on the target doping concentration TAC, but doping was more effective at lower TAC.