Machine vision inspection of early failure and line-shaped defects of blue InGaN/GaN light emitting diodes soaked in liquid nitrogen for cryogenic tests

• Published in: Results in physics Vol. 50; p. 106594
• Main Authors: Yang, Chun-Yen, Yu, Chih-Yuan, Lin, You-Li, Hon, Mou-Tuong, Yang, Shao-Jui, Zhang, Yi-Zong, Kang, Hsuan-Chia, Kuo, Yaw-Wen, Lin, Chia-Feng, Wu, You-Lin, Chou, Hsin-Hung, Chen, Hsiang, Li, Yung-Hui, Han, Jung
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2023; Elsevier
• Subjects: InGaN/GaN blue LED; Lattice deformation; Line defects; Liquid nitrogen; Machine vision; InGaN/GaN blue LED; Machine vision; Line defects; Lattice deformation; Liquid nitrogen
• ISSN: 2211-3797; 2211-3797
• DOI: 10.1016/j.rinp.2023.106594

•Cryogenic tests reveal spectral shifts in LEDs.•Line-shaped defects appear on GaN LED surface.•Machine vision detects early areas of degradation.•Reliability studies show promise for Space and Arctic applications. Cryogenic tests were conducted on blue InGaN/GaN light-emitting diodes (LEDs) by immersing the device in liquid nitrogen (LN2). To study the degradation of the LEDs, a combination of optical, electrical, and material characterizations were performed on the LN2-soaked device. The results indicate that noticeable emission spectral shifts were observed during the LED immersion due to lattice deformation. Moreover, clustering of cracks was generated in the cross-section, and line-shaped defects appeared on the surface of the GaN LED, which was different from the defects on AlInGaP LEDs after LN2 immersion. To track the trend of device damage, computer-assisted OpenCV-Python software was used to zoom in on nuanced variations in certain areas of the emission images. Early degradation of certain areas can be detected by computer-assisted machine vision, which has the potential to provide an early warning and protective circuits for the system consisting of the initial degraded LEDs. Reliability studies on LN2-soaked InGaN/GaN LEDs show promise in studying the reliability issues of GaN device applications in Arctic regions and space exploration.