Degradation mechanisms of InGaN/GaN UVA LEDs under swift heavy ion irradiation: role of defects

This work investigates the intrinsic degradation mechanism of InGaN/GaN UVA (320–400 nm) light emitting diodes (LEDs) after swift heavy ion irradiation from the defect aspect using temperature-dependent low frequency noise measurement. The UVA LEDs were exposed to 1423 MeV Ta ions with a fluence of 10⁸–10¹⁰ ions cm⁻². The optical power decreases and the leakage current increases evidently after irradiation. The defect behaviors were characterized to analyze the degradation mechanism. It is indicated that the ∼0.2 eV energy level defect decreases, and the defect with an energy level of about 0.65 eV increases with the increasing fluence, resulting in device degradation. Combining the defect energy level and the decreased yellow luminescence in the photoluminescence spectrum, the possible defect transform process is the newly created N interstitial atoms fill in the intrinsic V_Ga and form N_Ga after irradiation. (paper)