Control of aluminum doping of ZnO:Al thin films obtained by high-power impulse magnetron sputtering

► High quality ZnO:Al thin films by high-power impulse magnetron sputtering. ► Sputtering of an auxiliary Al electrode to control Al doping. ► Biasing potential of Al electrode controlled the Al content in ZnO:Al films. ► Optically transparent ZnO:Al films with minimum resistivity of 3.6´10-3 Ω´cm.