Current-driven degradation dynamics in GaN/InGaN multi-quantum-wells UV photodetectors fabricated with a high-quality Al2O3 passivation film

The degradation dynamics in GaN/InGaN multi-quantum-wells (MQWs) ultraviolet photodetectors (UV-PDs) submitted to high current stress have been intensively investigated. To scrutinize the root mechanism for degradation, several electro-optical measurements have been performed. The obtained results imply that (i) the rectification ratio diminishes largely after stress treatment, suggesting that leakage current and resistive effects are improved; (ii) both open-circuit voltage (VOC), and short-circuit current density (JSC) decline sharply within the first few hours (<50 h) of stress, after that degradation rates for VOC, and JSC slow down when stress time increases to 340 h, suggesting the physical processes responsible for degradation are altered after certain stress time; (iii) the spectral responsivity (Rλ), particularly at 384 (peak value) and below 347 nm reduce due to stress, indicating generation of deep levels associated with donors in n-GaN, and formation of severe point defects within MQWs lower the value of Rλ, whilst worsening of p-GaN quality ruin the detection capability below 347 nm; and (iv) the photo-response time changes due to acute carrier trapping during stress. Finally, the collected results suggest that the combined effects of activation of initially inactive defects and worsening of metal/GaN interfaces degrade the performance of UV-PDs during stress.