1. Introduction . UVB-LEDs exhibit various characteristics when applied as light sources, such as long lifespan, robustness, low energy consumption, high environmental friendliness, and mercury-free composition. AlGaN belongs to the wide-bandgap nitride semiconductor, considered as a new generation of semiconductors [ 1 ]. Due to its tunable direct bandgap, high breakdown field, and excellent chemical and thermal stability, AlGaN has played a crucial role in high-efficiency deep ultraviol...