Spectroscopy of a bulk GaN microcavity grown on Si(111)

We report the experimental observation of the exciton-photon strong coupling regime in a GaN microcavity. The structure has been grown by molecular beam epitaxy on a Si(111) substrate. The upper mirror is a SiO2/Si3N4 dielectric mirror and the silicon substrate acts as the bottom one. Angle resolved reflectivity and photoluminescence experiments have allowed to demonstrate the exciton-photon strong coupling regime, characterized by a Rabi splitting of 31 meV at 5 K. From the modeling of experiments, the oscillator strengths of excitons A and B are evaluated and compared to the values previously published. Then, the design of the bulk microcavity is optimized in order to maintain the strong coupling regime at room temperature; our calculations predict a Rabi splitting of 33 meV at 300 K in this case. A second kind of structure based on GaN/AlGaN quantum wells is also proposed, leading to an expected splitting,of 19 meV at 300 K.