Reliability issues in AlGaN based deep ultraviolet light emitting diodes

AlGaN based deep ultraviolet light emitting diodes (DUV LEDs) are key components in systems for air, water, and food purification and germicidal applications. Because of the heteroepitaxial growth of the DUV LED epilayers on sapphire, they have a large number of dislocations that invariably leads to a reduction of quantum efficiency and lifetime degradation. In this paper, we present our recent work at developing DUV LEDs with different device geometries, which includes a new micro-pixel electrode arrangement. This arrangement was used to study mechanisms responsible for their degradation. The micro-pixel device geometry with some new packaging schemes led to DUV LEDs with emission at 280 nm and lifetimes well in excess of 3000 hours. In this paper experimental details and the results of our study are presented.