Plasmonically-boosted exciton–photon coupling strength in a near-infrared LED based on a ZnO:Ga microwire/GaAs heterojunction with surface-coated Au&Ag alloy nanorods

Abstract

The development of electrically-driven low-dimensional coherent light sources via highly-polarized polariton emission behavior has been extensively researched, but suffers from limited modulation of the exciton–photon coupling strengths. Herein, an electrically-biased near-infrared exciton–polariton light-emitting diode (LED), which includes a Ga-doped ZnO microwire (ZnO:Ga MW) and p-type GaAs substrate, is demonstrated. The well-designed LED structure is conducive to producing strong coupling between excitons and cavity photons, thus yielding highly-polarized light-emissions due to the optical birefringence in the ZnO:Ga MW microcavity. In particular, when the LED device is modified using Au&Ag alloy nanorods (AuAgNRs) with desired plasmonic properties, the electroluminescence (EL) performance is significantly boosted, especially the Rabi-splitting energy, which increases from 96 to 285 meV. The current-injection exciton–polariton emission from the LED undergoing a strong coupling regime is confirmed through angle-resolved EL measurements. This study exhibits a performance-boosted near-infrared exciton–polariton LED at room temperature, which provides a new scheme toward the realization of highly energy-efficient polariton coherent light sources. Further, the significantly lower density of polariton states induced by the incorporated metal nanostructures highlights a bright future of realizing ultralow-threshold polariton lasers much more feasibly, in comparison to conventional lasers based on narrow bandgap semiconductors.