Abstract
The microcave array with extreme large aspect ratio was fabricated on the p-GaN capping layer followed by Ag nanoparticles preparation. The coupling distance between the dual-wavelength InGaN/GaN multiple quantum wells and the localized surface plasmon resonance was carefully characterized in nanometer scale by scanning near-field optical microscopy. The effects of coupling distance and excitation power on the enhancement of photoluminescence were investigated. The penetration depth was measured in the range of 39–55 nm depending on the excitation density. At low excitation power density, the maximum enhancement of 103 was achieved at the optimum coupling distance of 25 nm. Time-resolved photoluminescence shows that the recombination life time was shortened from 5.86 to 1.47 ns by the introduction of Ag nanoparticle plasmon resonance.
Highlights
Micro-emitters are widely used in micro displays, mask-free photolithography, highly parallel on-chip fluorescence detection and other fields
The localized surface plasmons (LSPs) coupling with the exciton in MQWs through its extended electro-magnetic field can occur in the near-field range and the effective transfer of energy between excitons in MQWs and surface plasmons (SPs) has a limited distance of approximately several tens of nanometers [4,13,18]
The penetration depth Z of the SP fringing electrical field into the semiconductor is given by Z = λ/2π[(ε GaN – ε metal)/ε metal2]1/2 where ε GaN and ε metal are the real parts of the dielectric constants of the semiconductor and metal and λ is the wavelength of the SP resonance
Summary
Micro-emitters are widely used in micro displays, mask-free photolithography, highly parallel on-chip fluorescence detection and other fields. It is difficult to experimentally evaluate the SP effect in high spatial resolution of a micro-LED. The LSPs coupling with the exciton in MQWs through its extended electro-magnetic field can occur in the near-field range and the effective transfer of energy between excitons in MQWs and surface plasmons (SPs) has a limited distance of approximately several tens of nanometers [4,13,18]. A more accurate experimental measurement is desired to investigate the optimal coupling distance and penetration depth of the SP field. We experimentally demonstrate a novel plasmonic LED configuration, incorporating microcave arrays structures with extremely large aspect ratio through the p-GaN layer covered by distributed Ag nanoparticles (NPs). Large aspect ratio enables us to measure the coupling distance dependent LSP effect with high accuracy
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