Over the last few years, research in the field of wide-bandgap semiconductors has shown impressive advancements, mainly due to the high importance of these materials for energy efficiency. Based on SiC and GaN, it is now possible to fabricate diodes and transistors with blocking voltages in the kV range with low on-resistance; such devices are expected to be rapidly adopted in the next generation of power conversion systems. This will permit reduction in power conversion losses, which will in turn have a positive economic and environmental impact, since conversion losses currently account for 10% of the global electricity consumption. However, before these technologies can significantly penetrate the market, further innovations in material and device architecture are needed. For example, (1) Several strategies are being explored for the fabrication of normally-off GaN-based transistors, but the stability and the reliability of the various solutions are still under debate; (2) The lack of native GaN substrates of large area and low cost limits the development of vertical transistors based on III-N materials; and (3) SiC transistors still suffer from threshold voltage instability and gate oxide reliability issues. Further, wide-bandgap semiconductors have also led to a revolution in the optoelectronics field: While GaN-based power LEDs are changing the world of lighting, new device architectures (nanowire devices, deep-ultraviolet LEDs, and laser diodes) are being studied and optimized. However, material-related aspects may significantly limit the efficiency of these devices, by inducing defect-related recombination, by limiting the extraction efficiency, and by reducing device reliability. This symposium will cover a broad range of material-related topics important to the development of wide-bandgap semiconductor power and optoelectronic devices; these issues are of high interest for the scientific community, since they limit the development of energy-efficient devices and deployment of the systems that depend on these devices.