Structural and electrical characteristics of ZnO thin films on polycrystalline AlN substrates

Fostered by the increasing use of AlN in highly thermally conductive electronic packages, it is attempted to grow ZnO thin films on polycrystalline AlN in the present work. Effects of the polycrystalline substrate on the structural and electrical properties of the ZnO films are highlighted. The ZnO films are synthesized by low-cost spin-coating technique from a precursor solution containing zinc acetate, 2-methoxyethanol, and monoethanolamine. Structural analysis was performed using X-ray diffraction, which showed all the films to be polycrystalline of hexagonal phase with no preferred orientation, in sharp contrast to numerous reports of strong c-axis orientation on glass substrates. The films, which were heat-treated at 700°C followed by firing in nitrogen containing 5% hydrogen at 500°C, exhibited better crystallinity and dense microstructure among all the samples and had the lowest resistivity (1.36 × 10^-1 Ω·cm). The minimum resistivity obtained in the present work is comparable to the values reported for the films grown using similar technique, thus indicating the negligible dependence of electrical properties on orientation of the films.