Optical and excitonic properties of ZnO films

Optical and excitonic properties of ZnO heterostructures are studied in order to observe the strong light-matter coupling in this material as it has been recently demonstrated in GaN. The optical index of ZnO is first studied as a function of wavelength through spectroscopic ellipsometric and reflectivity experiments on ZnO layers grown by molecular beam epitaxy and deposited on two different substrates: sapphire and silicon with an AlN buffer layer. The main features of the excitons: energy, oscillator strength and broadening are deduced. From the knowledge of these properties, a microcavity is then designed. The ZnO active layer is embedded between AlGaN/AlN and dielectric Bragg mirrors. The calculation of the reflectivity spectra as a function of the incident angle attests the strong coupling and a large Rabi splitting of 110 meV is expected in such a cavity.