Professor Emeritus Devki Talwar published "Anisotropic optical phonons in MOCVD grown Si-doped GaN/Sapphire epilayers" in the journal Materials Science & Engineering B.
Abstract
Micro-Raman spectroscopy is employed to study the anisotropic optical phonons of Si-doped GaN/Sapphir epifilms grown by metal organic chemical vapor deposition method. In an undoped 3.6 m thick sampleour polarized Raman measurements in the backscattering geometry revealed major first order modes of GaN and sapphire. Careful analyses of the second-order Raman spectra using critical-point-phonons from a rigid-ionmode fitted inelastic X-ray spectroscopy data with appropriate selection rules helped us attain expedient data for the lattice dynamics of GaN. In Si-doped films, a modified phonon confinement model is used for simulating Raman line shapes of Ehigh 2 phonons to monitor crystalline quality.