Role of surface treatments and localized surface plasmon nanoparticles on internal quantum efficiency of 800 nm diameter blue GaN/InGaN nano light emitting diodes

Arrays of nanorod multi-quantum-well (MQW) blue light emitting diodes (nLEDs) with diameter 800 nm were prepared by reactive ion etching (RIE) with subsequent surface treatment by KOH etching alone, and KOH etching followed by SiO₂ passivation with the SiO₂ prepared by the sol-gel technique. In addition, the effects of Ag/SiO₂ core/shell nanoparticles prepared by sol-gel were studied for all surface treatments. For as etched nLEDs, the Internal Quantum Efficiency (IQE) of photoluminescence was low, 5.5 %, because of the impact of surface damage introduced by RIE. KOH etching and KOH plus SiO₂ passivation produced an increase of IQE to respectively 5.7 and 6.8 %. When the Ag/SiO₂ core/shell nanoparticles known to produce localized surface plasmon resonance at the wavelength well-matched to the light emission from the MQWs were added to the polymer filling the gaps between the MQW nanorods, the result was found to depend on finding a proper balance between the enhancement due to the interaction Ag/SiO₂ nanoparticles adjacent to the MQW nanorods and the absorption by “idle” Ag/SiO₂ particles in the bulk of the polymer. When optimal concentrations of LSP NPs giving rise to maximal enhancement of the MQW PL intensity were used, a considerable improvement of performance was obtained, with IQE of 10.6 %.