Investigation of Failure Mechanism in AlGaN-Based Ultraviolet-C Light-Emitting Diodes Through 2-D Cathodoluminescence Analysis

This study delves into the intricate behaviors of degradation in AlGaN-based UV-C light-emitting diodes (LEDs) undergoing constant current stress and maintaining a constant heat sink temperature over a 500-h period. Employing 2-D cathodoluminescence (CL) at each degradation stage, we meticulously analyze the emissions from the multiple quantum wells (MQWs) layer and the N-AlGaN layer. The inclusion of peak wavelength mapping images and intensity distribution pseudo-color images adds depth to our understanding of defect generation and the decline of intensity across different layers throughout the degradation process. Complementing this analysis, the utilization of a focused ion beam and scanning electron microscope (FIB/SEM) allows us to visually inspect defects and observe the deterioration of the Cr/Al layer of the P-metal after 48 h of degradation. The results from CL emission align seamlessly with SEM images, offering a comprehensive visual methodology to pinpoint defect locations and analyze the failure mechanisms of ultraviolet-C (UVC) LEDs.