Enhanced light emission from AIGaN/GaN multiple quantum wells using the localized surface plasmon effect by aluminum nanoring patterns

We investigate the localized surface plasmon （LSP） effect by A1 nanorings on the AIGaN/GaN multiple quantum well （MQW） structure emitting at 365 nm. For this experiment, first, the size of A1 nanorings is optimized to maximize the energy transfer （or coupling） between the LSP and MQW using the silica nanospheres. Then, the Al nanorings with an outer diameter of 385 nm, which exhibit a strong absorption peak in the near-ultraviolet region, are applied to the top surface of the AIGaN/GaN MQW. The photoluminescence （PL） intensity of the MQW structure with AI nanorings increased by 227% at 365 nm compared to that without AI nanorings. This improvement is mainly attributed to an enhanced radiative recombination rate in the MQWs through the energy-matched LSPs by the temperature-dependent PL and time-resolved PL analyses. The radiative lifetime was about two times shorter than that of the structure without Al nanorings at room temperature. In addition, the measured PL efficiency at room temperature of the structure with A1 nanorings was 33%, while that of the structure without AI nanorings was 19%, implying that LSP-QW coupling together with the nanoring array pattern itself played important roles in the enhancement.