Accelerated life test of high luminosity AlGaInP LEDs

Specific tests to assess reliability of high luminosity AlInGaP LED for outdoor applications are needed. In this paper tests to propose a model involving three parameters: temperature, humidity and current have been carried out. Temperature, humidity and current accelerated model has been proposed to evaluate the reliability of this type of LED. Degradation and catastrophic failure mechanisms have been analyzed. Finally we analyze the effect of serial resistance in power luminosity degradation

High brightness GaN LEDs degradation during dc and pulsed stress

This paper reports an analysis of InGaN/GaN LEDs degradation under dc and pulsed current conditions. The analysis was carried out by means of current-voltage and optical power measurements, scanning electron microscopy and EDS maps. Identified degradation modes were leakage and generation/recombination current increase, series resistance increase and output power decrease, related to the high temperatures reached by the devices during stress. Failure analysis revealed degradation of anode contacts and Ti-W reflector, which can be related to the measured series resistance increase. Comparison between dc and pulsed stress carried out with the same average current indicated that pulsed driving does not imply an acceleration in the degradation rate, except for the lowest duty cycles