Degradation of InGaN-Based Leds Induced by 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) the mechanism responsible for reverse current conduction is tunneling; (ii) leakage current is correlated to the presence of reverse-bias luminescence (RBL); (iii) reverse current flows through a number of preferential paths, that can be identified by means of emission microscopy and can be correlated to the presence of structural defects; (iv) reverse-bias stress can induce an increase in the reverse-current of the LEDs, corresponding to a decrease in the breakdown voltage; (v) 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. These results can be relevant for understanding the reverse-bias ESD-failure of LEDs