Polarized Infrared Reststrahlen Features of Wurtzite InGaN Thin Film

Polarized infrared (IR) reflectance measurement was carried out to investigate the optical phonon modes of wurtzite structure In0.92Ga0.08N thin film grown by molecular beam epitaxy. Composition dependence of IR reststrahlen features was observed. Theoretical polarized IR reflectance spectrum was simulated using the standard multilayer optics technique with a multi-oscillator dielectric function model. By obtaining the best fit of experimental and theoretical spectrum, the Brillouin zone center E1 optical phonon modes together with the dielectric constant, layer thickness, free carriers concentration and mobility were extracted non-destructively. The extracted E1 optical phonon modes were compared with those generated from modified random element isodisplacement (MREI) model.