Defect structure of epitaxial GaN films determined by transmission electron microscopy and triple-axis X-ray diffractometry. - Metzger, T.; Hopler, R.; Born, E.; Ambacher, O.; Stutzmann, M.; Stommer, R.; Schuster, M.; Gobel, H.; Christiansen, S.; Albrecht, M.; Strunk, H. P. (Philosophical Magazine A, 1998)