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Detailed Program
Paper Number : LD-O03 |
Time Frame : 11:59~12:11 |
Presentation Date : Thurse day, 27, November |
Session Name : LED and Display Materials |
Session Chair 1# : In-Hwan Lee |
Session Chair 2# : Motoaki Iwaya |
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Enhanced optical output power of InGaN/GaN blue LED |
Hansu CHO |
Chonbuk National University |
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Light-emitting diodes (LEDs) that are considered as the next generation light source in general lighting applications, are currently being actively studied in order to increase their optical power and efficiency [1]. LEDs on patterned sapphire substrate (PSS) have a reduced threading dislocation (TD) density and improved light extraction efficiency, the latter due to additional scattering on patterned cone shape profile of the PSS substrate. This led to the use of such LEDs in commercial production [2]. In this study, high efficiency InGaN/GaN blue LED embedded with SiO2 nano-particles was fabricated on PSS. Nano-pillar (NP) GaN was fabricated by a dry etching using a self-assembled Ni nano-dots on a n-GaN layer grown on PSS by a metalorganic chemical vapor deposition (MOCVD). SiO2 nano-particles (100 nm in diameter) were embedded in the NP GaN template by spin-coating method. InGaN/GaN LED structure was overgrown over this template, as shown in Figure 1. Regrown GaN film could be overgrown only on NP GaN tips because the embedded SiO2 nano-particles acted as epitaxial lateral overgrowth mask facilitating selective lateral overgrowth, resulting in the formation of the air voids between nano-pillars. Light output powers of overgrown LEDs with SiO2 embedded in nano-pillar (SiO2-NP) on PSS have increased by 10 % compared with conventional LEDs on PSS. This result is attributed to the improvement of internal quantum efficiency caused by decreased TD density and relaxed strain due to the NP GaN, also to the increased light extraction efficiency due to additional scattering in the SiO2-NP structures.
Figure 1 (a) A schematic illustration of the SiO2-NP LED, (b) L-I characteristics of the conventional LED and SiO2-NP LED
References:
[1] V. V. Lysak, J. H. Kang, and C. -H. Hong, Appl. Phys. Lett. 102 (2013) 061114.
[2] S. R. Xu, P. X. Li, J. C. Zhang, T. Jiang, J. J. Ma, Z. Y. Lin, and Y. Hao, J. Alloys Comp. 614 (2014) 360.
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Acknowledgements : This research was supported by National Research Foundation of Korea(NRF) funded by Ministry of Science, ICT & Future Planning (2013R1A2A2A07067688, 2010-0019626) |
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