Resonant absorption and scattering suppression of localized surface plasmons in Ag particles on green LED

Abstract

The metallic-structure dependent localized surface plasmons (LSPs) coupling behaviors with InGaN QWs in a green LED epitaxial wafer are investigated by optical transmission, scanning electron microscopy (SEM) and photoluminescence (PL) measurements. Ag nanoparticles (NPs) are formed by thermal annealing Ag layer on the green LED wafer. SEM images show that for higher annealing temperature and/or thicker deposited Ag layer, larger Ag NPs can be produced, leading to the redshift of absorption peaks in the transmission spectra. Time resolved PL (TRPL) measurements indicate when LSP-MQW coupling occurs, PL decay rate is greatly enhanced especially at the resonant wavelength 560 nm. However, the PL intensity is suppressed by 3.5 folds compared to the bare LED. The resonant absorption and PL suppression are simulated by three dimension finite-difference-time-domain (FDTD), which suggests that Ag particle with smaller size and lower height lead to the larger dissipation of LSP.

The Coupling Behavior of Multiple Dipoles and Localized Surface Plasmons in Ag Nanoparticles Array

“…Therefore, although the LSP-dipole coupling leads to an enhancement of the dipole spontaneous emission, whether the IQE value would be suppressed or enhanced depends on the ratio of the dissipated energy to scattered energy. Furthermore, it is obvious that the ratio is determined by the size and morphology of the Ag NPs [5]. The light extraction efficiency (LEE) is determined by the ratio of the total upward radiation power P upper (collected from monitor 4) to the total scattered power P scat (from monitor 3) of this system.…”

“…Such coupling as a new path of recombination can increase the spontaneous emission rate [2], so that it is promising for the applications in solid-state lighting under high injection level and visible light communication [3,4], since most nonequilibrium carriers in QWs are excited by LSP, and the coupled energies would be finally extracted out as propagating photons in free space, and dissipated in Ag nanoparticles (NPs) by free electron oscillation and creation of electron-hole pairs. The proportion of the dissipated energy to extracted energy of LSP and multiple quantum well (MQW) coupling will determine either enhancement or suppression of the emission efficiency [5]. Many approaches have been proposed to decrease the dissipated energy by LSP, such as the metal morphology adjustment [6], distance optimization between the quantum well and metal particles [7], coupling among LSPs in neighbor metal particles [8], excitation of the LSP-QW system by e-beam in cathodoluminescence (CL) [9], and coupling of both the radial and orbital dipoles with LSP [10,11].…”

Internal quantum efficiency enhancement of GaInN/GaN quantum-well structures using Ag nanoparticles

“…Despite the matching of the extinction or resonance peak of sample B with the emission wavelength, sample C is expected to have a higher scattering capacity at the emission wavelength due to its larger average Ag NP sizes relative to sample B. 30,33 This is because the scattering-to-absorption ratio of sample C is higher than B due to the larger Ag NPs. As such sample C is scattering dominated and sample A is absorption dominated, while sample B is in between these limits.…”

Investigation of surface-plasmon coupled red light emitting InGaN/GaN multi-quantum well with Ag nanostructures coated on GaN surface

“…It can be clearly observed that the PL intensity for InGaN QW with as-deposited Ag film is lower than that for InGaN QW without Ag film due to the absorption of Ag film. 25 By thermal annealing at 350 C in a flowing N 2 ambient for 10 min, the PL intensity for InGaN QW with naked Ag NS is only slightly enhanced. However, with a 400 nm SiO 2 layer coated on the Ag NS, the integrated PL intensity of InGaN QW with SP-coupling is increased by 53% due to the elimination of the partial oxidation of Ag NS.…”