Deterioration of near-UV GaN-based LEDs in seawater vapour

•Near-UV LEDs were stressed in sea water vapour.•V-shaped etching groves were observed in cross sections.•Dark spots were found on the emission areas.•Na and Cl element compositions were inside the device after stress. Reliability investigations were conducted after GaN-based LEDs were stressed in seawater vapour. Multiple electrical, optical, and material analyses on the fine nanostructures of the LED were examined. Results indicate that dark spots on the surface and etching trenches observed on the cross section might damage the quantum well and degrade LED performance. Dissolved sodium ions might diffuse and punch through the quantum well and be responsible for these spots and trenches.