Photoluminescence of exciton-polaritons in GaN

Temperature dependent studies of the resonant (no-phonon) and phonon-assisted radiative recombination of free excitons (FEs) in GaN are performed, and are analyzed within the polariton concept. The parameters of the exciton–phonon coupling are estimated by analyzing the thermal broadening of the no-phonon (NP) FE line. The interaction with acoustic phonons is shown to be the dominant broadening mechanism for temperatures lower than 150 K, while for higher temperatures the contribution from the interaction with optical phonons is important. Strong defect/impurity scattering of exciton-polaritons is proposed to be responsible for the revealed unusual behavior of the free A exciton in GaN, i.e. an enhanced intensity of NP FE emission in comparison with its longitudinal optical (LO) phonon replicas, as well as the narrow line shape of the 1-LO assisted transitions.