Controlled growth of well-aligned ZnO mirco/nanorod arrays on GaN substrates using a novel solution method

This work reports on the controlled growth of well-aligned ZnO micro/nanorod arrays at low temperature on GaN substrates. The influence of GaN surface morphology and doping on the growth of ZnO rods via hydrothermal method is studied. The structural properties of ZnO rods are investigated using field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The grown ZnO rods show preferred orientation along the c-axis and are well aligned with high aspect ratios. For precisely controlling the formation of well-aligned ZnO micro/nanorod arrays, a two-dimensional periodic polymer aperture arrays on top of GaN is also utilized for selective growth of ZnO rods. The size of ZnO rods is controlled over a considerably wide size range from 130 nm up to 3.5 μm in diameter by tuning the aperture size of the pattern and solution concentrations. It is observed that the ZnO rods are not grown directly through the aperture template. In addition, the size of ZnO rods is found to be dependent on the geometry of polymer aperture arrays. The detailed growth behavior is characterized and analyzed. This work provides a route to achieve the low-temperature heteroepitaxy of ZnO mirco/nanorod arrays on GaN, which can be very useful for many optoelectronics applications, especially for light emitting diodes.