Optical properties of plasma-assisted molecular beam epitaxy grown InN/sapphire

• We prepared InN/sapphire films by plasma assisted molecular beam epitaxy (PA-MBE).
• Films are characterized by photoluminescence (PL), Raman scattering (RS) and infrared (IR) reflectance techniques.
• Our PL study consistently exhibited lower InN band gaps – indicating electron concentration dependent energy shifts.
• The RS phonon modes in InN/sapphire films are in good agreement with the grazing inelastic X-ray scattering.
• Effective medium theory is used to explain the IR spectra of InN/sapphire films and to estimating free charge carrier concentrations.

The optical properties of as-grown InN/sapphire films prepared by plasma assisted molecular beam epitaxy (PA-MBE) are characterized by photoluminescence (PL), Raman scattering (RS) and infrared (IR) reflectance techniques. The PL measurements have consistently exhibited lower values of InN band gaps providing clear indications of electron concentration dependent peak energy shifts and widths. The phonon modes identified by RS are found to be in good agreement with the grazing inelastic X-ray scattering measurements and ab initio lattice dynamical calculations. An effective medium theory used to analyze IR reflectance spectra of InN/sapphire films has provided reasonable estimates of free charge carrier concentrations.