Synthesis and characterizations of zinc oxide nanorods by cost effective aqueous hydrothermal technique for solid state lighting applications

Abstract

Zinc oxide (ZnO) is recognized as the most promising and often utilized semiconducting material due to its exceptional physical, chemical, optical, and relatively low-cost production features, as well as its ecologically beneficial nature. ZnO is a prominent candidate owing to its wide band gap (3.37 eV at room temperature) as well as its high exciton binding energy (60 meV) for the next generation of ultraviolet and blue optoelectronic devices. This would be achieved through the development of hybrid heterostructured LED devices with low manufacturing costs by blending gallium nitride (GaN) with zinc oxide (ZnO), which serves as the most efficient opto-electronic device. Due to its high electron mobility, high transparency in the visible wavelength spectrum, and low work function, ZnO is also a highly investigated transparent conducting oxide thin film for several applications. Besides, their incredible optical capabilities, ZnO-based optical devices, such as light-emitting diodes (LEDs) and laser diodes (LDs), have drawn a great deal of interest. This reported research work demonstrates the growth of high-density, high-aspect-ratio ZnO nanorod (NR) arrays on p-type gallium nitride substrates employing low-cost facial aqueous hydrothermal syntheses with optimised growing conditions. Additionally, a top-down chemical etching technique is adapted for fabricating zinc oxide nanotubes. High-quality ZnO nanorods with high intensity that were a few microns long were found across the GaN substrate with FESEM analysis. The chemical composition of the grown nanorods is confirmed with EDAX analysis. The wurtzite crystalline structure and c-axis orientation of the grown ZnO NR-arrays were identified in X-ray diffraction studies. A Schimadzu UV–Vis–NIR spectrophotometer was used to record the optical curve, and the energy gap was determined to be 3.24 eV by plotting the Tauc curve. The good optical quality of the harvested nanorods is ensured by the narrow near-band-edge (NBE) emission at 384 nm and defect emission peaks detected through photoluminescence analyses. Grown specimens are also subjected to Raman spectrum analyses, and the obtained results are presented.