Free-carrier response and lattice modes of group III-nitride heterostructures measured by infrared ellipsometry

We report on the application of infrared spectroscopic ellipsometry (IR-SE) for wavelengths from 3 to 30 mu m as a novel approach for nondestructive o ptical characterization of free-carrier and optical-phonon properties of gr oup III-nitride heterostructures grown by metal-organic vapor phase epitaxy on sapphire. Model calculations for the ordinary (epsilon(perpendicular to )) and extraordinary (epsilon(parallel to)) dielectric functions of the het erostructure components provide sensitivity to the IR-active phonon frequen cies and anisotropy of the free-carrier response.