Phonon-assisted polariton effects in near-band-edge optical emissions of single- and poly-crystal ZnO

The photoluminescence (PL) spectra of ZnO in the near-band-edge region were studied using the single- and poly-crystal samples with and without undergoing annealing in the forming gas or pure O-2. Substantial evidence revealed that the PL line at similar to 3.324 eV appears only in single-crystal samples and the PL lines at similar to 3.310 eV are enhanced in poly-crystal samples. Based on the determination of zero-phonon-lines, the marked difference between the PL spectra of single- and poly-crystal ZnO was ascribed to the polariton effects of A and B excitons, which originate from the interband scattering of exciton polaritons. (C) 2019 The Japan Society of Applied Physics