High-Efficiency InGaN/GaN Light Emitters Based on Nanophotonics and Plasmonics

We report novel methods to enhance light emission efficiencies from InGaN/GaN quantum wells (QWs) based on nanophotonics and plasmonics. First, the nanoscopic optical properties were observed and characterized based on the carrier localization and the quantum confinement Stark effect depending on the In composition of InGaN. Based on the results, we proposed that the emission efficiencies should be improved by making nanostructures, and showed actual enhancement of photoluminescence (PL) intensities by using fabricated random nanodisk and arrayed nanopillar structures. Moreover, surface plasmon (SP) coupling technique was used to enhance blue and green light emissions from InGaN/GaN QWs. We obtained a 14-fold increase in the PL intensity along with a 7-fold increase in the internal quantum efficiency (IQE) of light emission from InGaN/GaN when nanostructured Ag layers were deposited 10 nm above the QWs. The possible enhancement mechanism was discussed and reproduced by using the 3-D finite-difference time-domain simulations. Electron-hole pairs in InGaN QWs couple to electron oscillations at the metal surface and produce SPs instead of photons or phonons. This new path increases the spontaneous emission rate and the IQEs. The SP-emitter coupling technique would lead to superbright and high-speed solid-state light-emitting devices that offer realistic alternatives to conventional fluorescent light sources.