Polariton effects in reflectance and emission spectra of homoepitaxial GaN

Abstract

Reflectance and photoluminescence spectra of exciton polaritons in GaN homoepitaxial layers, grown by metalorganic chemical-vapor deposition on GaN single crystals, are reported. Polariton modes involving excitons $A,$ $B,$ and $C,$ which correspond to split valence bands of ${\ensuremath{\Gamma}}_{9},$ ${\ensuremath{\Gamma}}_{7},$ and ${\ensuremath{\Gamma}}_{7}$ symmetries, are resolved. Energies of the transverse excitons are found to be, respectively: ${E}_{\mathrm{TA}}=3.4767\mathrm{eV},$ ${E}_{\mathrm{TB}}=3.4815\mathrm{eV}$ and ${E}_{\mathrm{TC}}=3.4986\mathrm{eV},$ at the temperature $T=1.8\mathrm{K}.$ The shape of the measured emission spectra depends upon donor concentration. This is explained in terms of interbranch polariton scattering.