Enhanced Luminescence of GaN-based Light-Emitting Diodes with a Localized Surface Plasmon Resonance

초록

This research is about the development of GaN-based light-emitting diode with a gold nano-particles arrayed layer for increasing the light output. To realize high efficient solid-state lighting, the improvement of the light output is essential. In a conventional planar light-emitting diode, the efficiency is limited to several percents by a low light extraction efficiency due to the total internal reflection (TIR) at each boundaries [left side of Fig. 1] [1]. In order to enhance light extraction efficiency, various methods, such as surface texturing [2,3], photonic crystal [4], Surface Plasmon [5], and lift-off of sapphire substrate [6], have been tried. In this research, we use gold nano-particles for enhancing the light extraction efficiency. Gold nano-particles induce a Localized Surface Plasmon Resonance (LSPR) [7]. This effect performs extracting the trapped light in a device, and then, enhances the luminous efficiency of LEDs [right side of Fig. 1]. A gold nano-particles arrayed layer is fabricated by sputtering and annealing processes [Fig. 2]. The size and filling factor of particles can be controlled by the three conditions, such as a sputtered film thickness, annealing temperature and time. These are important factors to determine the efficiency, because a Localized Surface Plasmon Resonance depends on both of the size and density of particles [8, 9]. We fabricate the conventional LEDs by general fabrication methods, such as mesa etching of GaN using a Cl2-based plasma gas, indium tin oxide (ITO) transparent electrod sputtering, p- and n-electrodes deposition using lift-off process [Fig. 3]. After the patterning of gold nano-particle arrayed layers with various features, dependences of Surface Plasmon resonance wavelength on the two above mentioned factors are investigated. The spectroscopic and electro-luminescent characteristics of fabricated LSPR LEDs with various structured gold nano-particles will be discussed.