Impact of current-induced degradation process on the electro-optical characteristics of InGaN/GaN multiple-quantum-well photodetectors fabricated on sapphire substrate

• Published in: Applied Physics Letters Vol. 118; no. 2
• Main Authors: Dalapati, Pradip, Yamamoto, Kosuke, Egawa, Takashi, Miyoshi, Makoto
• Format: Journal Article
• Language: English; Japanese
• Published: Melville AIP Publishing 11.01.2021; American Institute of Physics
• Subjects: Applied physics; Carrier density; Current leakage; Defects; Degradation; Gallium nitrides; Indium gallium nitrides; Optical measurement; Optical properties; Photometers; Quantum efficiency; Quantum wells; Sapphire; Substrates
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/5.0027127

The impact of defects on the degradation behaviors of InGaN/GaN multiple-quantum-well photodetectors submitted to dc current stress has been intensively studied. The root mechanism for degradation has been studied employing combined electro-optical measurements. The collected results indicate that (i) stress can induce an increase in parasitic current leakage paths and trap-assisted tunneling in reverse and subturn-on forward bias ranges, respectively; (ii) during stress, the overall capacitance increases and localization improves in the apparent carrier concentration within the active region; (iii) stress causes a significant decrease in quantum well intensity and an increase in yellow luminescence; (iv) stress induces an increase in the external quantum efficiency due to broadening of the space-charge region; and (v) the detectivity of the device decreases after the stress treatment. These results suggest that degradation is largely attributed to the activation of initially inactive defects, mainly Mg–H, C-related, and VGa defects in the investigated devices, with consequent worsening of their performances.