Reliability of InGaN-based LEDs submitted to reverse-bias stress

This paper describes a study of the electro-optical characteristics and of the degradation of green LEDs submitted to reverse-bias stress. The results of this work indicate that: (i) under reverse-bias, the dominant conduction mechanism is tunnelling, and LEDs can show a weak luminescence signal (reverse-bias luminescence, RBL); (ii) reverse-current flows through localized preferential paths, that can be identified by means of emission microscopy; (iii) reverse-bias stress can induce a significant increase in the reverse-current of the LEDs, corresponding to a decrease in the breakdown voltage, and an increase in reverse-bias luminescence; (iv) the degradation rate has a linear dependence on the stress current level, suggesting that degradation is determined by the flow of accelerated carriers through pre-existing defects. -500 μA 100 μA Electroluminescence micrograph of one of the analyzed green LEDs under reverse bias (left) and forward bias (right). At the center of the LED there is no significant light emission, due to the presence of the bondpad