Keywords: near UV LEDs, reliability, reverse bias stress, water vapour, Au diffusion, gold diffusion, failure mechanisms, near ultraviolet LEDs, light–emitting diodes, deformation, metal contact, electromigration, gallium nitride, aluminium, GaN
Exploring failure mechanisms of near ultraviolet AlGaN/GaN light–emitting diodes by reverse–bias stress in water vapour
Reliability tests of GaN near UV light–emitting diodes (LED) were investigated by reverse–bias stress in water vapour. Various electrical, optical and material characterisations were performed to examine degradation trend and failure mechanism. On the basis of multiple material analyses, including scanning electron microscopy (SEM) with focus ion beam (FIB), energy dispersive X–ray spectrometry (EDX) and secondary ion mass spectroscopy (SIMS), deformation of the metal contact and the electromigration of Au could cause the increase of the leakage and reverse–bias electroluminescence, indicating some damaged high electric areas might be generated, which lead to LED failures. The characterisation techniques might resolve the long–term LED failure reasons. Furthermore, the reverse–bias LED operations are promising for short–time screening of the Near UV LED quality for future industrial applications.