Research on renewable energy technologies has been intensified from the past decade due to the scarcity of fossil fuels and global warming caused by the by-products from the consumption of fossil fuels. Hydrogen generation from solar water splitting is one of the promising routes to secure sustainable, green, storable and portable form of energy. Gallium nitride-based alloys, such as InGaN, are attractive for solar water splitting due to their tunable band gap properties, ranging from far infrared (InN≈0.7 eV) to ultraviolet (GaN≈3.4 eV) based on alloy composition that can absorb the entire solar spectrum. Further, GaN exhibit good crystal quality and stability against chemical, photo corrosion and UV irradiation which are requisites for solar water splitting. In addition, nanostructures made from these materials offer great advantages such as enhanced sunlight absorption, increased surface area and improved carrier separation which are critical for photocatalytic applications.
In this talk, I will discuss the formation of GaN nanopillars by using inductively coupled reactive ion etching (ICP-RIE). The assessment of optical quality of as-fabricated GaN nanopillars by using micro-photoluminescence measurements will be presented. The photoluminescence results will be explained by using finite difference time domain (FDTD) simulations. GaN planar and nanostructures were used as a photoanodes in photoelectrochemical (PEC) cells for solar water splitting applications. The influence of doping concentration, diameter and length of nanopillars on PEC performance of GaN nanopillar photoanodes will be discussed. Further, I will present my future research work plans, including the development of InGaN/GaN multiple quantum well nanostructure and GaN/ZnSe core-shell structure photoanodes to extend light absorptions to visible range of solar spectrum, and the realization of direct solar water splitting using GaN based semiconductors.