The degradation mechanism of GaN-based Near-ultraviolet (NUV, 320-400 nm) light emitting diodes (LEDs) with low-indium content under electrical stress was studied from the aspect of the defect. A decrease of the optical power, and an increase of the leakage current were observed after electrical stress. The defect behaviors were characterized using deep level transient spectroscopy (DLTS) measurement under different filling pulse widths. After stress, a defect with the energy level of 0.47-0.56 eV increases, accompanied by a decrease of 0.72-0.84 eV defect. Combing the defect energy level with the increased yellow luminescence in photoluminescence spectral, the device degradation can be attributed to the activation of the gallium vacancy and oxygen related complex defect along dislocation, which was previously passivated with hydrogen. This study reveals the evolution process of defects in the time dimension under electrical stress and their spatial location, laying a foundation for the manufacture of GaN-based NUV LEDs with high reliability.
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