A comparative study of growth and properties of atomic layer deposited transparent conductive oxide of Al doped ZnO films from different Al precursors

Transparent conducting oxide of Al-doped ZnO (AZO) films were prepared by atomic layer deposition (ALD) using diethylzinc (DEZ) and 3 kinds of Al precursors, including trimethylaluminum (TMA), aluminum isopropoxide (AIP) and AlCl3. The impact of ZnO/Al2O3 cycle ratios from 9:1 to 39:1 and Al precursors on the growth rate, Al dopant concentration, structure, and resistivity of AZO films were investigated deeply. At the same ZnO/Al2O3 cycle ratio, the film thickness decreases and the Al dopant concentration increases gradually with TMA, AIP and AlCl3 precursors in turn. Generally, the Al doping leads to poorer crystallinity and better conductivity for AZO films. Both TMA-AZO and AIP-AZO films with 19:1 ZnO/Al2O3 cycle ratio show the lowest resistivity of 3.3-4 × 10− 3 Ω cm with Al doping content of 2.1% and 2.3%, respectively, which can be well explained by the effective field model. Additionally, all the AZO films exhibit great optical transparency of > 85% for wavelengths of 370-900 nm.