Understanding the degradation processes of GaN based LEDs submitted to extremely high current density

Abstract

This work presents the first analysis of the degradation mechanisms induced by extremely high current densities on green InGaN-based LEDs. To this aim, bare-chip LEDs were submitted to current step-stress, until catastrophic failure. We identified a current density threshold, around 260A/cm2, beyond which the devices start degrading, showing an increase in leakage current both in reverse and forward bias regimes. Moreover, a current crowding effect was detected on the degraded samples by electroluminescence measurements. A lumped element model was developed to describe the effects of stress. Results suggest that localized power dissipation, due to high current density flow under the anode pad, induces the formation of shunt paths and, eventually, leads to the catastrophic failure of the LEDs.