Among oxide materials, zinc oxide (ZnO) has outstanding optical and electronic properties, such as large exciton-binding energy, excellent luminescent properties, high electron mobility, piezoelectricity, and a direct wide bandgap. All of these features and the relatively easy growth of ZnO nanostructures have spurred the investigation of these materials for a large scope of photonics and electronics applications, including light-emitting diodes (LEDs), photodetectors, and transparent field-effect transistors.