Abstract
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.
Highlights
Semiconductor microcavities (MCs) have been intensely investigated recently as a solid-state cavity quantum electrodynamics system [1, 2]
The strong exciton-photon coupling at room temperature (RT) in bulk ZnO-based hybrid MCs has been demonstrated according to the excellent agreement between experimental and theoretical angle-resolved reflectivity spectra
It is found that the upper polariton branches (UPBs) could not be experimentally probed in the thick bulk ZnO MCs since the Rabi splitting energy is larger than the exciton binding energy, pushing the UPB into the energies of scattering states absorption
Summary
Semiconductor microcavities (MCs) have been intensely investigated recently as a solid-state cavity quantum electrodynamics system [1, 2]. Microcavity polaritons are boson like at low densities, and have extremely light in-plane effective mass These unique MC exciton-polariton properties are very important for the study of the fundamental physical phenomena including strong light-matter interaction [3], solid-state cavity quantum electrodynamics [1], and dynamical Bose-Einstein condensates [4, 5]. Polariton dynamics in similar GaN-based MCs were investigated, where a relaxation bottleneck was observed at RT and the relevant mechanisms have been discussed [14, 15]. We report the experimental observation of strong coupling regime in bulk ZnO-based hybrid MCs. Theoretical and experimental study of the effects of exciton scattering states on polariton dispersions are discussed at RT. The relevant mechanisms leading to the possible presence of a polariton bottleneck in ZnO MCs are discussed
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