A Raman spectroscopy study of InN

Abstract

We report on the Raman analysis of InN films grown by molecular beam epitaxy (MBE), RF sputtering and remote-plasma enhanced chemical vapor deposition (RPE-CVD). Varying the excitation wavelength, information on the homogeneity of the InN films and the free carrier concentration is extracted. The use of UV Raman spectroscopy to probe excess nitrogen in the InN films via a Raman band located around 2300 cm −1 is illustrated. RF sputtered InN was found to contain significantly more excess nitrogen than MBE and RPE-CVD grown InN. The use of resonant Raman scattering spectroscopy to contribute information to the current controversy of the InN band gap is proposed and first results are presented. Resonant Raman scattering under 1.49 eV excitation suggests the presence of a critical point in the InN band structure within 200–300 meV of this laser excitation energy. Further investigations will be needed to clarify whether this is the band gap or a higher critical point in the band structure.