On the mechanism of carrier recombination in downsized blue micro-LEDs

• Published in: Scientific reports 2021-11, Vol.11 (1), p.22788-22788, Article 22788
• Main Authors: Chen, Po-Wei, Hsiao, Po-Wen, Chen, Hsuan-Jen, Lee, Bo-Sheng, Chang, Kai-Ping, Yen, Chao-Chun, Horng, Ray-Hua, Wuu, Dong-Sing
• Format: Article
• Language: English
• Subjects: 639/166; 639/301; 639/624; 639/766; 639/925; Defects; Emissions; Genetic screening; Humanities and Social Sciences; Light emitting diodes; multidisciplinary; Photolithography; Plasma etching; Recombination; Science; Science (multidisciplinary); Silicon dioxide
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-02293-0

The mechanism of carrier recombination in downsized μ-LED chips from 100 × 100 to 10 × 10 μm 2 on emission performance was systemically investigated. All photolithography processes for defining the μ-LED pattern were achieved by using a laser direct writing technique. This maskless technology achieved the glass-mask-free process, which not only can improve the exposure accuracy but also save the development time. The multi-functional SiO 2 film as a passivation layer successfully reduced the leakage current density of μ-LED chips compared with the μ-LED chips without passivation layer. As decreasing the chip size to 10 × 10 μm 2 , the smallest chip size exhibited the highest ideality factor, which indicated the main carrier recombination at the high-defect-density zone in μ-LED chip leading to the decreased emission performance. The blue-shift phenomenon in the electroluminescence spectrum with decreasing the μ-LED chip size was due to the carrier screening effect and the band filling effect. The 10 × 10 μm 2 μ-LED chip exhibited high EQE values in the high current density region with a less efficiency droop, and the max-EQE value was 18.8%. The luminance of 96 × 48 μ-LED array with the chip size of 20 × 20 μm 2 exhibited a high value of 516 nits at the voltage of 3 V.