Study of the aluminum doping of zinc oxide films prepared by atomic layer deposition at low temperature

Highlights: ► This paper shows a possibility to improve the aluminum doping of atomic layer deposited zinc oxide at low temperature. ► The influence of purge lengths on the properties of the material is evidenced. ► Changes in the optical properties of the material induced by the aluminum doping are studied. - Abstract: This study presents the effect of purge pulses conditions on the electrical and optical properties of zinc oxide films doped with aluminum and grown by ALD at low temperature (160 °C). Undoped ZnO films showed a clear improvement of the carrier concentration when purges were lengthened, which suggests that this purge lengthening causes a higher defect related doping. It was also showed that this purge lengthening leads to a further increase of the carrier concentration in the case of ZnO:Al films attributed to a better spatial repartition of the Al dopants in the film. The evolution of optical properties was also studied and compared to the electrical properties highlighting free carrier absorption and a Burstein–Moss shift. An abnormal modification of the optical properties was observed when the aluminum content in the film was increased.