Exciton–polariton light-emitting diode based on a single ZnO superlattice microwire heterojunction with performance enhanced by Rh nanostructures

Abstract

One-dimensional (1D) wirelike superlattice micro/nanostructures have received considerable attention for potential applications due to their versatility and capability for modulating optical and electrical characteristics. In this study, 1D superlattice microwires (MWs), which are made of undoped ZnO and Ga-doped ZnO with periodic and alternating crystalline layers (ZnO/ZnO:Ga), were synthesized individually. Under optical excitation, a series of resonance peaks in the photoluminescence spectrum can be ascribed to polariton emission, which originates from the coupling interaction of the 1D photonic crystal and confined excitons along the wire direction. Using a p-type GaN layer as the hole transport layer, a kind of waveguide light source based on an individual ZnO/ZnO:Ga superlattice MW was proposed and constructed. By analysing the spatially resolved electroluminescence spectra, the observed multipeak was ascribed to exciton–polariton emission with a vacuum Rabi splitting of about 275 meV. Cladding with Rh nanostructures gives rise to appropriate ultraviolet plasmons, and the Rabi splitting energy of our device was enhanced up to 413 meV. The exciton–polariton properties were further examined using angle-resolved electroluminescence measurements. Therefore, individual superlattice MWs can act as optical microresonators to achieve photon–exciton coupling with a large Rabi splitting energy. The experimental results indicate that an individual ZnO/ZnO:Ga superlattice MW can be generally used in developing exciton–polariton luminescence/lasing light sources, particularly for constructing low-threshold/thresholdless lasers toward pragmatic applications.