Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 54: Nano-optics of metallic and semiconducting nanostructures (experiments II)
O 54.9: Vortrag
Donnerstag, 26. März 2009, 17:00–17:15, SCH A216
Enhanced LED emission by metal nanoparticles — •Tino Göhler1, Andreas Hille1, Stefan Grafström1, Lukas M. Eng1, and Reiner Windisch2 — 1Technische Universität Dresden, 01069 Dresden, Germany — 2OSRAM Opto Semiconductors GmbH, 93055 Regensburg, Germany
The external quantum efficiency of light emitting-diodes (LEDs) based on AlGaAs is limited by internal total reflection because of the of high refractive index (n=3.6). Metal nanoparticles (MNPs) can be used as dipole scatterers in order to enhance the emission of LEDs.
We investigate the enhancement produced by single gold MNPs onto red LEDs (λemission = 645 nm FWHM=20 nm) by using a confocal imaging set-up. The enhancement depends strongly on the particle size and on the surrounding medium (air n=1.0, immersion oil n=1.5). While in air particles of all sizes investigated (80-150 nm) enhance the LED emission, we observed a strong size dependence when embedding the particle in immersion oil. Here, the surrounding medium shifts the plasmon resonance of the particles such that it overlays the LED emission spectrum for larger particles. Then absorption leads to suppression rather than enhancement of the emission.