Soft and Hard Failures of InGaN-Based LEDs Submitted to Electrostatic Discharge Testing

This letter reports an extensive analysis of the degradation mechanisms of InGaN-based light-emitting diodes (LEDs) submitted to reverse-bias electrostatic discharge (ESD). The results of this analysis indicate that two different failure modes, namely, “soft” and “hard” degradations, can be induced by ESD pulses. The “soft” failure mode takes place as a consequence of ESD events with moderate voltage/current levels and consists in a decrease in the reverse-bias leakage current of LEDs. This effect is due to the annihilation of some of the defective paths responsible for leakage-current conduction, possibly triggered by the injection of relatively high reverse-bias current densities. “Hard” failure takes place when high-voltage/current ESD pulses are applied to an LED. After hard failure, LEDs behave as short circuits. This process is due to the high voltage levels reached by the junction during an ESD event (with subsequent dielectric rupture) or to the injection of extremely high current densities through one of the localized paths responsible for reverse-current conduction.