Effects of electron–phonon interaction and chemical shift on near-band-edge recombination in GaN

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Abstract
A coherent analysis of the near-band-edge luminescence spectra of undoped and Si-doped GaN layers grown by metalorganic vapor phase epitaxy on a sapphire substrate has been performed with a model including the effect of the charge carrier–longitudinal optical (LO) phonon interaction, based on Fröhlich’s polaron theory. This model allows one to correlate the relative intensities of the phonon sidebands to the position of the zero-phonon line from which ionization energies are obtained. Moreover, central-cell corrections are taken into account using two different models: the quantum defect model and the Lucovsky model [Solid State Comm. 3, 299 (1965)]. The effect of the electron-LO phonon interaction has been included in these models. Comparison between theory and experiment through the Huang-Rhys factor [Proc. Roy Soc. A204, 406 (1950)] allows a precise determination of the impurity binding energies and effective radii, as well as a reliable characterization of the charge carrier–LO phonon interaction.

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