Abstract
High-resolution X-ray diffraction, temperature-dependent photoluminescence (PL), time-resolved PL, and positron annihilation spectroscopy are employed to investigate the degradation mechanism of InGaN/GaN multiple quantum wells (MQWs) light-emitting diodes (LEDs) under silicon ion irradiation. Reduction of the quantum-confined Stark effect due to crystalline strain relaxation, enhancement of indium localization due to thermal spike, generation of nonradiative recombination centers (NRCs), and carrier removal effect due to atom displacement are revealed to be critical factors in LEDs postirradiation performance. New NRCs are proven to be the main reason for the degradation of the internal quantum efficiency of MQWs. The increase of the threshold voltage and leakage current in LEDs are caused by the carrier removal effect and new defects in bandgap induced by radiation. In addition, new NRCs are found to appear earlier than indium localization and carrier removal effect with increasing silicon ion fluence. Atom displacement defects are revealed to be located mainly in p-type GaN and MQWs layers. Radiation-induced nitrogen vacancies are considered compensation donors in p-type GaN, whereas all other nitrogen and gallium-related defects are NRCs in MQWs.
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