Recent advances and challenges in AlGaN-based ultra-violet light emitting diode technologies

The lighting industry undergoes a revolutionizing transformation with the introduction of III-nitride semiconductors, and “LEDs” became a household name. The solid-state light source GaN/InGaN replaced incandescent and compact fluorescent lamps. The UV region (∼200−400 nm) has yet to see this paradigm shift. The UV region comprised of AlN/AlGaN, possess unexpected problems such as high dislocation density leading to poor internal quantum efficiency, difficulty in achieving high concentration of hole, causing problems in the injection efficiency of carriers, anisotropy in optical polarization with increased Al content. Throughout this article, the major bottlenecks in achieving highly efficient UV LEDS has been discussed. Special attention has been given to highlight better techniques of crystal growth, many design aspects, difficulties in fabrication technologies, modern nanostructured materials and devices, and much more on the efficient light extraction. Finally, we addressed UV-LED degradation characteristics, which is paramount from the end-user perspective.