Controlling the defect density to improve the output power of InGaN/GaN-based vertical light-emitting diodes by using substrates patterned with SiO2 lenses |
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Authors: | Daesung Kang Da-Som Kim Sun-Kyung Kim Kiyoung Song Myunghoon Jung Hwanhee Jeong |
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Affiliation: | 1. LED Division, LG Innotek Co. Ltd, Paju-city, Korea;2. Department of Nanophotonics, Korea University, Seoul, Korea;3. Department of Applied Physics, Kyung Hee University, Yongin-si, Korea |
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Abstract: | In this study, we investigated the effect of SiO2 lenses on the output power of InGaN/GaN-based vertical light-emitting diodes (VLEDs; wavelength = 445 nm) and compared the results to those of reference VLEDs without the SiO2 lenses (planar samples). Arrays of SiO2 lenses (pitch = 3 μm, width = 2.5 μm, height = 1.0 μm) were formed on c-plane sapphire substrates. The external quantum efficiency (EQE) of the packaged VLEDs with planar and patterned substrates was characterised. At 5 mA, the EQE of the patterned samples was 150% higher than that of the planar samples. A patterned, N-polar, n-GaN sample contained far fewer nanopipes (approximately 2.2 × 105 cm?2) than a planar n-GaN sample (approximately 2.4 × 106 cm?2). Furthermore, the patterned samples contained far fewer threading dislocations (approximately 1.0 × 108 cm?2) than the planar samples (approximately 5.0 × 108 cm?2). Scanning electron microscopy (SEM) images showed that the photoelectrochemical (PEC)-etched patterned samples contained cones that were 150% larger than that of the PEC-etched planar samples. In addition, SEM images, cathode luminescence measurements and finite-difference time-domain simulations were used to characterise the improved light output of the patterned samples. |
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Keywords: | GaN light emitting diode line defects patterned substrate external quantum efficiency structural analysis |
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