Infrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers

摘要

Infrared reflection spectroscopy is applied to statehyphen;ofhyphen;thehyphen;art thin film heterostructures of grouphyphen;III nitrides on sapphire and Si substrates. The individual layers of GaN and AlGaN and the AlN buffer layer are identified by their phonon frequencies. Under nonhyphen;perpendicular incidence of the light, A1(LO) phonon modes are observed in the wurtzite system. The presence of the very thin AlN buffer layer manifests itself in clear features of the AlN phonons. The A1(LO) phonon mode energy is determined in AlxGa1minus;xN forxape;0.15. Raman spectra confirm our findings. copy;1996 American Institute of Physics.