| Optical properties of modified light-emitting diodes structures using localized surface plasmons |
| Jin-Hyeon Yun |
| Chonbuk National University |
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Keywords: Light emitting diode, localized surface plasmon, nanostructure, optical properties
Surface plasmons (SPs) are coherent electron oscillations that exist at a metal/dielectric interface. Specifically, the SPs in noble metal nanoparticles (NPs) embedded in a dielectric matrix are called localized surface plasmons (LSPs).[1] These LSPs have been studied for applications in sensing, medical imaging, and surface enhanced spectroscopy. It has been demonstrated that LSP phenomena can also be utilized to enhance the light output of GaN/InGaN multi-quantum well (MQW) structures and GaN/InGaN MQW light emitting diodes (LEDs). For the LSP enhancement to be efficient, the NP layer should be placed in close proximity to the active MQW region of the device, generally no further than ~100 nm.[2] The thickness of the spacer layer between the active region of LED and the LSP region is a serious concern, with the thickness of the p-GaN emitter layer in contemporary LEDs more or less fixed by the spreading resistance and junction performance considerations and difficult to alter. The spacer thickness for effective LSP coupling has been already reported, and the effective distance of the Ag nanostructure from the active layer of LEDs should be within several tens of nanometers. However, in conventional blue LED structures the thickness of the p-type GaN spacer layer is generally greater than 76 nm in order to form a well-behaved p–n junction and to provide reasonably low spreading resistance. Such a GaN thickness is too large for the effective LSP coupling process.
As a solution to the problem posed by the high thickness of n-GaN and p-GaN layers of conventional LEDs, we proposed the fabrication of metal NPs embedded in InGaN/GaN nanopillar LEDs and hole-patterned LEDs. In such a structure, the NPs could be placed very close to the active layer of the nanopillar LEDs and hole-patterned LEDs. In this work, photoluminescence behavior of Ag@SiO2 NPs embedded nanopillar LED structures and hole-patterned LEDs structures and the effect of surface plasmons on InGaN/GaN nanopillar LED and hole-patterned LEDs with Ag@SiO2 NPs were investigated and discussed. We demonstrate that the approach taken does indeed allow to achieve a strong enhancement of light output as demonstrated in Fig. 1.
References:
[1] W. L. Barnes, A. Dereux, and T. W. Ebbesen, Nature, 424 (2003) 824.
[2] K. Okamoto, I. Niki, A. Shvartser, Y. Narukawa, T. Mukai, and A. Scherer, Nature Mater., 3 (2004) 601. |
| 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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