P. Disseix

Determination of the refractive indices of AlN, GaN, and AlxGa1−xN grown on (111)Si substrates

The refractive indices of several AlxGa1−xN alloys deposited on silicon are determined by ellipsometry and reflectivity experiments at room temperature. The AlGaN layers are grown on (111)Si substrate by molecular-beam epitaxy on top of an AlN/GaN/AlN buffer in order to reduce the strain of the alloy. The Al composition is deduced from energy dispersive x-ray spectroscopy and photoluminescence experiments. The refractive index n and the extinction coefficient k are determined in the 300–600 nm range. For the transparent region of AlxGa1−xN, the refractive index is given in form of a Sellmeier law.

Strong light-matter coupling at room temperature in simple geometry GaN microcavities grown on silicon

The reflectance spectra of simple design GaN-based microcavities have been studied in the 5 K–300 K range. The epitaxial structure consists of the silicon substrate and the stack of buffer layers as the back mirror, a GaN active layer, and a 100 A thick aluminium layer as the top mirror. Active layer thicknesses of λ∕2, λ, or 3λ∕2 were investigated. The samples with GaN thicknesses λ∕2 and λ display an anticrossing behavior between the cavity and exciton modes, with measured Rabi splittings of 47 and 60 meV, respectively, both at 5 K and room temperature.

Experimental observation of strong light-matter coupling in ZnO microcavities: Influence of large excitonic absorption

We present experimental observation of the strong light-matter coupling regime in ZnO bulk microcavities grown on silicon. Angle resolved reflectivity measurements, corroborated by transfer-matrix simulations, show that Rabi splittings in the order of 70 meV are achieved even for low finesse cavities. The impact of the large excitonic absorption, which enables a ZnO bulk-like behavior to be observed even in the strong coupling regime, is illustrated both experimentally and theoretically by considering cavities with increasing thickness.

Fabrication and characterization of a room-temperature ZnO polariton laser

A ZnO planar optical microcavity displaying room-temperature polariton lasing over a wide range of cavity-exciton detunings has been fabricated. The cavity combines optimum crystalline quality, given by a ZnO single-crystal substrate, and optimum photonic quality, obtained by the use of two dielectric SiO2/HfO2 Bragg mirrors. A maximum cavity quality factor of about 4000 has been measured. Typically, the polariton lasing transition is accompanied by an increase of the output intensity by more than two orders of magnitude, a reduction of the emission linewidth and a relatively small blueshift of the lower polariton branch (less than 5% of the Rabi splitting).

Relaxation and emission of Bragg-mode and cavity-mode polaritons in a ZnO microcavity at room temperature

The strong coupling regime in a ZnO microcavity is investigated through room temperature photoluminescence and reflectivity experiments. The simultaneous strong coupling of excitons to the cavity mode and the first Bragg mode is demonstrated at room temperature. The polariton relaxation is followed as a function of the excitation density. A relaxation bottleneck is evidenced in the Bragg-mode polariton branch. It is partly broken under strong excitation density, so that the emission from this branch dominates the one from cavity-mode polaritons.

Growth by molecular beam epitaxy and optical properties of a Ten-period AlGan/AlN distributed Bragg reflector on (111)Si

This paper reports the growth of GaN, (Al,Ga)N and AlN layers on (111)Si substrates by molecular beam epitaxy using ammonia. Using proper conditions, GaN layers with threading dislocation densities as low as 5 x 10 9 cm -2 can be obtained on (111)Si. The structural and optical properties of GaN and (Al,Ga)N have been studied using electron microscopy, photoluminescence and reflectivity. In particular, the tensile strain has been assessed. Finally, a ten-period Al 0.2 Ga 0.8 N/AlN Bragg mirror has been grown, with a UV (340 nm) centered bandwidth of 35 nm and peak reflectivity of 78%.

LO-phonon-assisted polariton lasing in a ZnO-based microcavity

Polariton relaxation mechanisms are analyzed experimentally and theoretically in a ZnO-based polariton laser. A minimum lasing threshold is obtained when the energy difference between the exciton reservoir and the bottom of the lower polariton branch is resonant with the LO phonon energy. Tuning off this resonance increases the threshold, and exciton-exciton scattering processes become involved in the polariton relaxation. These observations are qualitatively reproduced by simulations based on the numerical solution of the semiclassical Boltzmann equations.

Influence of the mirrors on the strong coupling regime in planar GaN microcavities

The optical properties of bulk

Modelling of thermally detected optical absorption and luminescence of (In,Ga)N/GaN heterostructures

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Patterned silicon substrates: A common platform for room temperature GaN and ZnO polariton lasers

GaN microcavities working in the strong light-matter coupling regime are investigated using angle-dependent reflectivity and photoluminescence at 5 K and 300 K. The structures have an Al