Degradation of UV-A LEDs: Physical Origin and Dependence on Stress Conditions

This paper presents an extensive analysis of the degradation of UV-A light-emitting diodes (LEDs) submitted to constant current stress. The study is based on combined electrical, optical, and thermal measurements and demonstrates the following results: 1) the UV-A LEDs submitted to constant current stress show a gradual degradation, and the degradation rate is strongly dependent on the emission wavelength; 2) the degradation process is ascribed to the generation of point defects within the active region of the devices, with a subsequent increase in the nonradiative recombination rate; and 3) the time to degradation is strongly dependent on the stress current level and is thermally activated (activation energy equal to 0.36 eV).