InAlGaN/GaN heterostructures and thin films with In composition ranging from 0.03 to 0.1 are characterized by means of Raman scattering excited at various energies in the ultra violet range, tuning the laser excitation energy through the band gap of InxAlyGa1-x-yN. It is shown that the addition of In to the AlyGa1-yN alloy diminishes considerably the vibration energy of the A1(LO) phonon mode. The phonon line is asymmetric on the low energy side, and the asymmetry increases with In content, while the main peak shifts to lower energies. A shift of the phonon energy has also been observed when the excitation energy is close to the absorption edge of the InxAlyGa1-x-yN layer. The nature of this shift is discussed in relation with intrinsic and extrinsic inhomogeneities in the quaternary alloy.
Bibliographical notePublisher: Wiley Interscience