Effect of crystallinity of ZnO buffer layer on the properties of epitaxial (ZnO:Al)/(ZnO:Ga) bi-layer films deposited on c-sapphire substrate

► The lowest resistivity of 8.4 × 10−5 Ωcm was obtained at annealed buffered substrate. ► The characteristic of c-axis oriented texture grows up at different substrates. ► Two kinds of stacking faults were observed at Fourier filtered images. ► Origin and consequences of stacking faults were discussed. ► Lower defect density of film has a benefit effect on the resistivity.