Failure limits and electro-optical characteristics of GaN-based LEDs under electrical overstress. (September 2018) - Renso, N.
Abstract: This work presents the analysis of the degradation mechanisms and of the electro-optical characteristics of light emitting diodes (LEDs) submitted to electrical overstress. The analysis was carried out by a custom-setup, that allows us to measure the current-voltage (I-V) and electroluminescence curves of the devices while pulsing the devices with increasing voltages, up to failure. We investigated a wide span of electrical over-stress (EOS) time durations (from 1 ms to 10 s). The results provide information on (i) the dependence of failure voltage/power level on pulse duration; (ii) on the temperature-dependence of the pulsed I-V characteristics; and (iii) on the changes in electrical and optical properties reached at extremely high current densities. The results presented within this paper provide relevant (and so far unpublished) information on the characteristics of the devices in this extremely high stress regime. Highlights: Electrical over stress events induce strong power dissipation. Optical power increase is induced by thermally-assisted conduction mechanism. Above 2 kA/cm 2, non-radiative recombination starts to dominate on the radiative one. Extremely high current densities trigger current crowding effect. Radiative recombination in p-type material is detected at high current densities.