Ultraviolet (UV) light sources have a direct impact on everyone’s life. They are used\ua0to sterilize surfaces as well as for water purification. In addition, they are used in\ua0green houses to enhance health-promoting substances in plants, for phototherapy to\ua0treat skin diseases, for sensing and material curing. Today, most of these applications\ua0use mercury lamps that are fragile, bulky and toxic. AlGaN-based UV light-emitting\ua0diodes (LEDs) have the potential to solve all these issues, but their implementation\ua0has been limited due to their low electrical to optical power conversion efficiency\ua0(PCE) being below 10%. Blue-emitting GaN-based LEDs have already found their\ua0way into everyone’s home through general lighting. This was made possible by the tremendous performance improvements, reaching PCEs close to 90%. Unfortunately, the device concepts for achieving highly efficient GaN-based LEDs, such as the thin-film flip-chip (TFFC) design that can greatly improve light-extraction efficiency, are not easily transferred to AlGaN-based UV LEDs.In this work, we demonstrate a new device platform to realize UV LEDs with a\ua0TFFC design based on electrochemical etching to remove the substrate. In the first\ua0part of this work, electrochemical (EC) etching of AlGaN layers with a high Al content up to 50% was demonstrated, which enabled the separation of epitaxial LED\ua0layers from their substrate while maintaining the high quality of the active region.The second key technological step was the integration of EC etching in a standard\ua0UV LED fabrication process, which required protection schemes to prevent parasitic\ua0electrochemical etching of the LED structure and the development of a device design compatible with flip-chip bonding. Finally, this work was completed by the first\ua0demonstration of a TFFC UVB LED using electrochemical etching
