Lattice vibrations in hexagonal Ga1-xMnxN epitaxial films on c-plane sapphire substrates by infrared reflectance spectra

The lattice vibrations of undoped hexagonal Ga1-xMnxN (x from 0.0% to 1.5%) epitaxial films grown on c-plane sapphire substrates by metalorganic chemical vapor deposition have been investigated using infrared reflectance spectra in the frequency region of 200-2000 cm(-1) (5-50 mu m) at room temperature. The experimental reflectance spectra were analyzed using the Lorentz oscillator model for infrared-active phonon observed. The E-1(LO) phonon frequency slightly decreases with increasing Mn composition. However, the E-1(TO) phonon frequency linearly increases with the Mn composition, which can be well expressed by (558.7+350x) cm(-1) and the broadening values are found to be larger than that of the GaN film. It indicates that Mn incorporation decreases the peak values (from the E-1 phonon) of the infrared dielectric functions due to the local variation in the lattice constants and to the destruction of the crystal translational symmetry. (c) 2006 American Institute of Physics.