Analysis of the degradation of AlGaN-based deep-ultraviolet LEDs

The aim of this paper is (i) to give a description of the parametric and catastrophic degradation of AlGaN-based DUVLEDs, and (ii) to analyze the role of current and temperature in determining the degradation kinetics. The analysis was carried out on a wide number of DUV-LEDs with similar characteristics, emitting at 310 nm, and fabricated by Sensor Electronic Technology, Inc. The results indicate that (i) gradual degradation is correlated to the increase in the nonradiative recombination in the active region of the devices; (ii) stress determines an increase in the defect-related current components of the LEDs, possibly due to an increase in the concentration of defects in the active region; (iii) stress determines an increase in the operating voltage of the LEDs and a decrease in junction capacitance; (iv) the degradation kinetics are strongly dependent on the stress current level, while operating temperature has only a limited impact on the degradation rate; (v) during stress the devices can show catastrophic degradation, due to the generation of parasitic conductive paths in parallel to the junction, in correspondence of the mesa borders.