Topological analysis of defects in epitaxial nitride films and interfaces

The present work is a review of the topological theory of defects and inter faces in crystalline materials, aimed at illustrating cases that have been studied under this framework in nitride films and interfaces. The review ad resses crystallographic calculations in hexagonal and trigonal crystals usi ng the Frank system. It also presents the principal methods of a priori and a posteriori defect characterization in a unified manner, showing their eq uivalence, the circumstances under which they are applicable, and practical aspects of their deployment. A number of experimental observations are ana lysed, and useful conclusions are extracted, for example, concerning admiss ible defects, structure-mechanism relations, and the influence of defects o n properties. These include (i) threading, stacking-fault and interfacial d islocations in GaN epilayers, (ii) the influence of the epitaxial interface on the systematic appearance of inversion and stacking disorder, (iii) str uctural transformations of inversion domain boundaries due to their interse ctions with stacking faults, and (iv) double-positioning twinning in TiN co ntact layers deposited on GaN.