Failure Modes and Mechanisms of DC-Aged GaN LEDs

Abstract

This paper presents failure modes observed in long‐term aging of high‐brightness GaN/InGaN LEDs. The blue LEDs submitted to DC aging test present large decrease of emitted optical power and increase of diode reverse leakage current. Increase of parasitic series resistance, suggesting contact degradation, has also been found in stressed sample, together with apparent carrier density increases and reduction of the junction depletion width. Furthermore stressed LEDs present modification of a specific trap property: trap activation energy decreases from 340 meV in the virgin sample down to 75 meV in the stressed sample. Generation of non‐radiative recombination centers seems to be one of the dominant failure mechanisms responsible for the observed electrical and optical LED degradations.

Degradation of AlGaN-based ultraviolet light emitting diodes

“…This type of time dependence for device parameters during degradation is known and usually associated with diffusion. For example, it may be diffusion of contact metal to the device structure or diffusion of the dopant atoms [5].…”

Low-frequency noise sources in as-prepared and aged GaN-based light-emitting diodes

“…The degradation modes and stress-induced defects in GaN LEDs due to thermal, direct current ͑dc͒, and pulsed electrical stress have been investigated recently by dc current-voltage ͑IV͒ characterization, light-emission mapping, capacitance dispersion, and deep-level transient spectroscopy. [5][6][7] The light-emission decrease with aging has been correlated with an increase in contact resistance, leakage current, and specific changes in trap activation energies. 7 Low-frequency noise ͑LFN͒ characterization is known to be a sensitive tool to investigate the device quality and to track the changes in the structures with aging.…”

N-contacts degradation analysis of white flip chip LEDs during reliability tests

“…Past studies have mostly focused on vertical thin film LEDs (VTF LEDs) [7,8,10,11]. Menghini et al [7,8] and Meneghesso et al [10] conducted high thermal storage, direct current and Pulsed Width Modulation (PWM) stress tests.…”

“…Menghini et al [7,8] and Meneghesso et al [10] conducted high thermal storage, direct current and Pulsed Width Modulation (PWM) stress tests. Results show an increase of the forward voltage with stress time which the authors related to an increase of parasitic serial resistance and ideality factor of the LEDs.…”