Stokes/anti-Stokes Raman spectroscopy of Al_0.86Ga_0.14N semiconductor alloy

The lattice dynamics of a high Al composition semiconductor alloy, Al_0.86Ga_0.14N, in comparison with intrinsic GaN and AlN are studied by Stokes/anti-Stokes Raman spectroscopy in the temperature range of 85–823 K. The phonon anharmonic effect in Al_0.86Ga_0.14N is found to be stronger than that in GaN, revealing low thermal conductivity in the semiconductor alloy. Multi-phonon coupling behavior is analyzed by both Stokes Raman and anti-Stokes Raman spectroscopy. It is interesting to find that the anti-Stokes scattering exhibits stronger three-phonon coupling than the Stokes scattering, which may be due to the fact that the anti-stokes scattering process is generated from an excited state and the scattered photons have higher energies. The Stokes/anti-Stokes temperature correction factor β for Raman modes in Al_0.86Ga_0.14N alloy are all smaller than those of the corresponding intrinsic modes in GaN and AlN. The reasons for the difference in β can be attributed to three aspects, including the equipment setups, materials properties (the binding energy) and the coupling strength of Raman scattering and the sample.