| The wide band gap semiconductor GaN and related materials, with their excellent physical and chemical properties, have a very promising application potential for both high temperature electronic devices and green to UV light emitters. Development of nondestructive characterization techniques and determination of the optical responses of these optoelectronic materials are important for improving device design and fabrication. In this work, generalized and standard ellipsometric data acquisition methods were developed for sapphire, GaN/msapphire, and GaN/c-sapphire structures. The dependence of sample orientation, incident angle, surface roughness, and depolarization were also studied for the analysis of anisotropic optical responses. Coupled TO phonons were discovered from GaN on m-sapphire and were used for the determination of Euler angles in the VASE model. Dielectric functions of nitrides were described by simplified Adachi's model dielectric function based on their critical point structures. The strain effects of thin AIN film were studied by Raman scattering and x-ray diffraction. Electron concentration of Si doped GaAs epitaxial layer were determined by both Raman scattering and infrared ellipsometry. Characterization of Phonon structure, crystal orientation, crystal quality, doping effect, film thickness, surface roughness, thickness uniformity, interface structure, and anisotropic (ordinary and extraordinary) dielectric functions of sapphire, GaN, AlN and related III-nitrides are discussed in detail. |
