Efficiency and Catastrophic Failure of High-Power Blue GaN LEDs During Extremely High Temperature and Current Stress

Abstract

This paper reports an extensive analysis of the short-term effects of extremely high driving current on the performance and reliability of commercial high-power blue LEDs. To this aim, five different groups of devices, having different structures and chip areas, were submitted to increasing levels of bias current, until catastrophic failure was reached. For the first time we provide information (i) on the reliability limits of LEDs outside the safe-operating area, (ii) on the related failure processes, and (iii) on the impact of current and temperature in determining the degradation of the devices. In addition, the results of failure analysis indicate that for almost all devices, failure occurs in correspondence of a major current injection point, often determined by the presence of crowding phenomena. Failure is ascribed to the high localized power dissipation and temperature. Device layout and intrinsic defects may favour the observed degradation processes.