Abstract
Eu-doped GaN is a promising material for the active layer in red light emitting diodes. Although the output power of LEDs based on GaN:Eu has been increasing by a combination of structural and growth optimizations, there is still a significant limitation resulting from a poor light extraction efficiency, typical for high refractive index materials. Here we studied nanostructuring of the top of the optical active layer by nano-cubes for enhancement of the light extraction efficiency, and its effect on the optical emission characteristics. By etching nano-cubes into the active layer, we observed an increase in directional light output power of Eu(3+) ions of up to 60%, as well as a grating effect. Simultaneously, the absorption of excitation light into the optical active layer was improved, leading to a 12.8 times increase of output power per available Eu(3+) ion.