Oxygen interstitial mediated effective doping of Al in ZnO:Al films prepared by magnetron sputtering

• An oxygen interstitial (Oi) mediated doping effect in ZnO:Al films is reported.
• The concentration of Oi is tailored by varying the oxygen ratio in sputtering gas.
• The doping efficiency is increased by ~10% due to the Oi-mediated doping effect.

How to increase the doping efficiency in ZnO:Al (AZO) films is a longstanding question and a hard nut to crack. In the present work, we report an oxygen interstitial mediated doping effect for AZO films prepared by magnetron sputtering. The concentration of oxygen interstitials (Oi) in the as-grown films is tailored by changing the oxygen partial pressure during sputtering. Although the Al donors are temporarily passivated by Oi, they are easily reactivated through the removal of Oi by post-annealing in hydrogen at 500 °C. Our results show that the as-grown film which has the highest Oi concentration turns out to have the highest carrier concentration after hydrogen annealing, and the doping efficiency is increased by ~10% because of the oxygen interstitial mediated doping effect. We infer that although Oi deactivate Al donors in the as-grown films, they favor the distribution of the doped Al at the atomic level and the formation of Al substituting at Zn sites (AlZn), and thus, increase the effective Al donors after hydrogen annealing.

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