GaN hybrid microcavities in the strong coupling regime grown by metal-organic chemical vapor deposition on sapphire substrates

We observe exciton-photon strong coupling at low and room temperature in the ultraviolet spectral region in a GaN-based one wavelength bulk microcavity. The hybrid cavity is composed of 25 pairs of epitaxially grown Al0.2Ga0.8N/Al0.6Ga0.4N distributed Bragg reflectors (DBRs) on the lower side of the cavity and 9 pairs of Si3N4/SiO2 as the upper mirror, to obtain cavity Q values up to 160. Anticrossing is observed between the cavity mode and the bulk GaN exciton, showing the formation of polariton modes with normal mode splitting of 43 meV. The lower polariton dispersion is observed in both reflectivity and photoluminescence, with good agreement between the two obtained over a large tuning range of 40 meV. Good fits are obtained to the spectra of the Bragg mirrors. From simulations it is found that the reflectivity spectra of the Bragg mirrors are not significantly limited by absorption in the Al0.2Ga0.8N layers. (C) 2007 American Institute of Physics.