Temperature dependence of Raman scattering in hexagonal indium nitride films

We report on Raman spectroscopy study of hexagonal InN thin films grown by metal-organic vapor-phase epitaxy, with the emphasis on frequencies and linewidths of E-2(high) and A(1)(LO) modes in the temperature range from 93 to 443 K. The present InN exhibits a fundamental band gap of similar to 1.2 eV from photoluminescence and optical transmission spectra, which is in good agreement with the recent suggested parameter for intrinsic InN. The temperature dependence of the E-2(high) and A(1)(LO) phonons can be described well by a model which has taken into account the contributions of the thermal expansion of the crystal lattice, the strain between InN thin films and sapphire substrates, as well as three- and four-phonon coupling. Micro-Raman mapping results also demonstrate the high uniformity of the studied InN. (c) 2005 American Institute of Physics.