Strong light-matter coupling in bulk GaN-microcavities with double dielectric mirrors fabricated by two different methods

Abstract

Two routes for the fabrication of bulk GaN microcavities embedded between two dielectric mirrors are described, and the optical properties of the microcavities thus obtained are compared. In both cases, the GaN active layer is grown by molecular beam epitaxy on ͑111͒ Si, allowing use of selective etching to remove the substrate. In the first case, a three period Al 0.2 Ga 0.8 N / AlN Bragg mirror followed by a / 2 GaN cavity are grown directly on the Si. In the second case, a crack-free 2 m thick GaN layer is grown, and progressively thinned to a final thickness of . Both devices work in the strong coupling regime at low temperature, as evidenced by angle-dependent reflectivity or transmission experiments. However, strong light-matter coupling in emission at room temperature is observed only for the second one. This is related to the poor optoelectronic quality of the active layer of the first device, due to its growth only 250 nm above the Si substrate and its related high defect density. The reflectivity spectra of the microcavities are well accounted for by using transfer matrix calculations.

Polariton condensation phase diagram in wide-band-gap planar microcavities: GaN versus ZnO

“…In the present study polariton lasing is investigated well below this limit, in the range from a few W/cm² to 300 W/cm². Furthermore in the GaN MC investigated in this work, the condition requested to reach the SCR is fully satisfied since the Rabi splitting value is larger than the inhomogeneous excitonic broadening (Ω>>σ) 52,53 . In this sample the inhomogeneous excitonic broadening deduced from the fit of the half cavity reflectivity spectrum (figure A2b) is equal to 10±3 meV for A and B excitons.…”

All-dielectric GaN microcavity: Strong coupling and lasing at room temperature

“…1,2 As electrical injection into ZnO and organic based microcavities is technologically challenging, GaN based microcavities operating in the strong coupling regime are currently considered as the most promising candidates for implementation of such robust, ultra-low threshold, room temperature polaritonic laser devices. [3][4][5][6][7] Several crucial factors, namely, the requirement for high finesse optical cavities and uniform pumping in the active region of GaN microcavities have yet to be fully addressed. 8 The former drastically reduces the lasing threshold of polariton lasers, 9 whilst the latter, as recent optical pulsed and quasi-CW pumping experiments show, 10,11 is necessary to obtain the relatively high carrier densities required for lasing, particularly in an electrically pumped device.…”

Fabrication and Optical Properties of a Fully-Hybrid Epitaxial ZnO-Based Microcavity in the Strong-Coupling Regime

“…Two different conceptions of ZnO microcavities have been reported: all oxide structures with high quality factors but polycrystalline zinc oxide layers [5][6][7], or hybrid cavities with a better quality of the active layer but a reduced photonic confinement [2,[8][9]. Similar to previous works on GaN-based microcavities [10,11] a third approach can be followed using two dielectric mirrors after removal of the substrate used for the epitaxy of the active layer for a high quality factor and a reduced inhomogeneous broadening of the ZnO excitons.…”