Size dependent characteristics of AlGaN-based ultraviolet micro-LEDs

AlGaN-based deep ultraviolet LEDs have attracted significant interest as a reliable and efficient disinfection technology to combat the pandemic outbreaks. However, EQEs of commercial DUV LEDs is currently low. One of the bottlenecks that limit the overall efficiency is the low light extraction efficiency (LEE), which is <15% for conventional flip chip devices. Many attempts have been made to increases the LEE, such as using thin (or no) absorbing p-GaN layer or fabricating novel microstructures, which often result in significant increase in the forward voltage or involve costly processing steps. $\mu\text{LEDs}$ have been proved to increase the LEE in visible wavelength devices but there are a few reports on the size dependence characteristics in the DUV range [1]–[2]. Additionally, $\mu\text{LEDs}$ can prevent the current crowding present in large UV LEDs since growing a thick and conductive n-AlGaN on AlN templates without relaxation remains a challenge.