It is well accepted that point and extended defects play an important role on the properties of III-V nitride semiconductors. It is also essential to understand the defect formation mechanisms to obtain the necessary material control to reach the full realization of the technological potential of the wide bandgap material system. Due to the nature of the centers involved a detailed and extensive investigation must be performed in controlled samples. In this work, results obtained using a combination of defect-sensitive techniques employed to detect, identify, and verify the role of defects and impurities in the structural, optical, and electronic properties of thick freestanding GaN, bulk AlN, and homoepitaxial layers are reviewed. The sharpness and line-shapes of XRD and Raman scattering lines of AlN and GaN were employed as figures of merit to evaluate the crystalline quality and homogeneity of the bulk and epitaxial layers. Detailed luminescence studies of AlN and GaN, grown by different techniques, and homoepitaxial films show evidence of the pervasive nature of some defects.

Keywords: GaN, AlN, bulk, Raman scattering, XR diffraction, photoluminescence, cathodoluminescence, homoepitaxial