Effect of Trap Behavior on Recombination in AlGaN-Based UV-C LEDs Degradation

The trap behavior and its effect on recombination in the degradation of AlGaN-based deep ultraviolet light-emitting diodes (LEDs) under constant current stress are investigated in this work. The Shockley Read Hall (SRH) recombination of vacancies plays a significant role in the degradation of the device, and the trap-assisted radiative recombination also has a certain contribution. The increase in vacancies comes from two mechanisms: 1) the degradation of the lattice under stress and 2) the release from the associated complex of vacancies that exist in the fresh device under stress. The impact of vacancies on device degradation also has two mechanisms: 1) act as a non-radiative recombination center and participate in SRH recombination and 2) form complexes with the acceptor impurities under stress and enhance trap-assisted radiative recombination. These failure mechanisms severely affected by current expansion in large-area devices. The increase of nitrogen/gallium vacancies and vacancies-magnesium complexes and the decrease in native vacancy complexes and interfacial states are speculated according to deep level transient spectrum and admittance spectroscopy. This study provides an in-depth analysis of the defect behavior and recombination induced by electrical stress in UV-C LEDs and suggests possible optimization directions for the fabrication of high-reliability AlGaN-based large-area devices.