Influence of growth temperature on the electrical and structural characteristics of conductive Al-doped ZnO thin films grown by atomic layer deposition

Al-doped ZnO thin films (AZO) were deposited by atomic layer deposition at various temperatures (100-300 °C) with a frequency ratio of 19/1 (Zn-O/Al-O), and their properties were evaluated. With increasing growth temperature, the Al contents in the AZO thin films were continuously increased, because of the rapid increase in the incorporation efficiency of the Al-O layer with respect to the Zn-O layer. Although low-temperature deposition resulted in the abnormal [100]-preferred orientation of the AZO films, they had a high carrier density of ~ 1020 cm3. However, the Hall mobility showed a low value of 1.5 cm2/Vs due to the high density of impurities such as C-O or O-H caused by incomplete reaction for precursors. In contrast, the electrical and structural properties of the AZO thin films were enhanced by increasing growth temperature, due to the increased Al doping level and reduced residual impurities, which was confirmed by X-ray diffraction and X-ray photoelectron spectroscopy.