Epitaxy of Zn2TiO4 (1 1 1) thin films on GaN (0 0 1)

High-permittivity spinel Zn2TiO4 thin films were grown on GaN (0 0 1) by rf-sputtering. Grazing-angle, powder, and pole-figure X-ray diffractometries (XRD) were performed to identify the crystallinity and the preferred orientation of the Zn2TiO4 films. Lattice image at the Zn2TiO4 (1 1 1)/GaN (0 0 1) interface was obtained by high-resolution transmission-electron microscopy (HR-TEM). An oxygen atmosphere in sputtering and post heat-treatment using rapid thermal annealing effectively enhanced the epitaxy. The epitaxial relationship was determined from the XRD and HR-TEM results: (1 1 1)Zn2TiO4||(0 0 1)GaN(1 1 1)Zn2TiO4||(0 0 1)GaN, (2 0 2¯)Zn2TiO4||(1 1 0)GaN,and[2 1¯ 1¯]Zn2TiO4||[0 1¯ 1 0]GaN. Finally, the relative permittivity, interfacial trap density and the flat-band voltage of the Zn2TiO4 based capacitor were ∼18.9, 8.38 × 1011 eV−1 cm−2, and 1.1 V, respectively, indicating the potential applications of the Zn2TiO4 thin film to the GaN-based metal-oxide-semiconductor capacitor.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► High-permittivity spinel Zn2TiO4 thin films were grown on GaN (0 0 1) by sputtering. ► Oxygen atmosphere and post heat-treatment annealing effectively enhanced epitaxy. ► The epitaxial Zn2TiO4 modifies the dielectric properties of ceramic oxide.