Analysis of surface plasmon mediated light emitting diode efficiency enhancement

The extraction of light from current light emitting diodes (LEDs) is very low due to the large index of refraction mismatch between the semiconductor and dielectric interface resulting in a small percentage of light escaping the LED As a result of this problem a new solution is necessary for improving the photon extraction efficiency from LEDs. One solution that is explored in this paper is the use of the extraordinary optical transmission phenomenon in which the amount of light passing through a diffraction limited aperture is greater than expected. This effect is most often associated with periodically perforated metal films. This metal film also has the potential to be used as the carrier injector superstrate to reduce the effects of carrier density gradients when driving LEDs at high currents. In this paper, the fundamental properties of the extraction efficiency problem will be defined and the current density gradient problem is experimentally verified. A theoretical background on the surface plasmon phenomenon is then explored and a subsequent analysis of the transmission characteristics of an infinitely thin perfectly conducting periodically perforated metal film is explored. It is then shown what effects thickness have on the periodically perforated metal film and how it affects the surface plasmon prorogation. Finally, an analysis of how quantum well based LEDs can further improve the performance of the efficiency by directly coupling radiative recombinations to surface plasmon modes