Performance enhancement of GaN-based light emitting diodes by the interaction with localized surface plasmons

Abstract

The effects of localized surface plasmons (LSPs) on the enhancement of photoluminescence and electroluminescence efficiency of GaN-based light-emitting diode (LED) structures are reviewed. It is shown that the LSPs formed by metal nanoparticles (NPs) or by local thickness variations of the metal films can contribute to the enhancement of light emitted by LED structures under optical or electrical excitation. The problems of choosing a suitable metal for such LSPs in the given spectral range are discussed. Various approaches to incorporating the LSP NP films into the LED structures are analyzed. The issues specific to different spectral ranges (blue, green, UV) are described. The wavelength range for which the application of LSP particles can be useful depends on the metal used, the shape and dimensions of the particles, and on their density and distribution. Roughly, as a first order approximation, it is concluded that Ag is in general the best material for the blue spectral region, Au is best for the green region, and Al is most suitable for the UV region. It is demonstrated that core/shell Ag/SiO2 NPs for the blue region have serious advantages in terms of stability over Ag NPs. For blue LEDs it is found that the most important factor is the suppression of the efficiency droop with increasing LED output power. For green and UV regions the most important factor is the strong influence of the non-radiative recombination channels. In addition, for the UV LEDs the increased light extraction efficiency is also an important issue. It is shown how LSP NPs can provide efficient means to combat these problems.