Resonant Raman spectroscopy on InN

The novel use of resonant Raman spectroscopy to elucidate the band gap of InN is illustrated in a study of MBE-grown films. This technique can distinguish between electronic transitions related to the InN from transitions related to defects and impurities that are so typical for current InN material. Using excitation energies from 1.49 eV (830 nm) to 2.54 eV (488 nm), we identify a critical point in the InN band structure within approximate to 200-300 rneV below 1.5 eV. The origin of this critical point, whether band gap or higher critical point, is discussed. Furthermore, Raman results are presented on the temperature dependence of the InN phonons. Analysis of the data provides information on phonon lifetimes and decay mechanisms, important to assess whether hot phonon effects need to be considered in future InN devices.