The strong light-matter interaction within a semiconductor high-Q microcavity has been used to produce half-matter/half-light quasiparticles, exciton-polaritons. The exciton-polaritons have very small effective mass and controllable energy-momentum dispersion relation. These unique properties of polaritons provide the possibility to investigate the fundamental physics including solid-state cavity quantum electrodynamics, and dynamical Bose-Einstein condensates (BECs). Thus far the polariton BEC has been demonstrated using optical excitation. However, from a practical viewpoint, the current injection polariton devices operating at room temperature would be most desirable. Here we report the first realization of a current injection microcavity GaN exciton-polariton light emitting diode (LED) operating under room temperature. The exciton-polariton emission from the LED at photon energy 3.02 eV under strong coupling condition is confirmed through temperature-dependent and angle-resolved electroluminescence spectra.

Wide-band gap ZnO semiconductors are attractive materials for the investigation of microcavity exciton polaritons due to the large exciton binding energy and oscillator strength. We report the growth and characterization of bulk ZnO-based hybrid microcavity. The phenomenon of strong exciton-photon coupling at room temperature has been observed in the ZnO-based hybrid microcavity structure, which consists of 30 pair epitaxially grown AlN/AlGaN distributed Bragg reflector ͑DBR͒ on the bottom side of the 3 / 2 thick ZnO cavity and 9 pair SiO 2 / HfO 2 DBR as the top mirror. The cavity quality factor is about 221. The experimental results show good agreement with theoretically calculated exciton-polariton dispersion curves based on transfer matrix method. From the theoretical and experimental exciton-polariton dispersion curves with two different cavity-exciton detuning values, the large vacuum Rabi splitting is estimated to be about 58 meV in the ZnO-based hybrid microcavity.

Wide bandgap semiconductors are promising materials for the development of polariton-based optoelectronic devices operating at room temperature (RT). We report the characteristics of ZnO-based microcavities (MCs) in the strong coupling regime at RT with a vacuum Rabi splitting of 72 meV. The impact of scattering states of excitons on polariton dispersion is investigated. Only the lower polariton branches (LPBs) can be clearly observed in ZnO MCs since the large vacuum Rabi splitting pushes the upper polariton branches (UPBs) into the scattering absorption states in the ZnO bulk active region. In addition, we systematically investigate the polariton relaxation bottleneck in bulk ZnO-based MCs. Angle-resolved photoluminescence measurements are performed from 100 to 300 K for different cavity-exciton detunings. A clear polariton relaxation bottleneck is observed at low temperature and large negative cavity detuning conditions. The bottleneck is suppressed with increasing temperature and decreasing detuning, due to more efficient phonon-assisted relaxation and a longer radiative lifetime of the polaritons.

Here we report the first realization of a current injection microcavity GaN exciton-polariton light emitting diode (LED) operating under room temperature (RT). The hybrid microcavity structure consists of InGaN/GaN quantum wells sandwiched between bottom epitaxial DBR and top dielectric DBR. The anti-crossing behavior of polariton LED denotes a clear signature of the strong interaction between excitons and cavity photons.

The characteristics of exciton-polaritons in ZnO-based microcavities (MCs) are demonstrated with a large vacuum Rabi splitting due to large exciton binding energy and oscillator strength. The lower polariton branches (LPBs) can be clearly observed. For low temperature and large negative detuning conditions, a clear polariton relaxation bottleneck in bulk ZnO-based MCs has been observed in angle-resolved photoluminescence measurements from 100 to 353 K at different cavity-exciton detunings. The bottleneck is strongly suppressed with increasing the temperature and pumping power and reducing detuning. This observed results supposed to be due to more efficient phonon-assisted relaxation and a longer radiative lifetime of the polaritons. In addition, the linewidth broadening, blue-shift of the emission peak, and polarization of polariton lasing from below threshold to up threshold are also discussed.