ESD degradation and robustness of RGB LEDs and modules: An investigation based on combined electrical and optical measurements

This paper presents an extensive analysis of the robustness of state-of-the-art RGB LEDs and LED modules submitted to Electrostatic Discharges (ESD). We studied both single RGB LEDs, and small modules constituted by the series connection of 2, 3, and 4 monochromatic LEDs. ESD events were simulated by a Transmission Line Pulser (TLP), capable of generating voltage pulses with a duration of 100 ns and increasing amplitude: after each of the pulses the electrical and optical parameters of the devices were monitored, with the aim of describing the effects of ESD events on the performance of the devices. The results indicate that: (i) the ESD robustness strongly depends on the LED wavelength; InGaN-based LEDs (the green and the blue LEDs) have a lower robustness with respect to the AlInGaP devices (i.e., red LEDs); (ii) non-destructive ESD events can induce significant modifications in the performance of the devices even below the failure voltage/current level; (iii) the ESD robustness of LED modules strongly depends on the robustness of each LED of the chain, and on the variability of the devices. The results presented in this paper provide important information for the design of high robustness multi-LED systems.