Pyramidal defects in metalorganic vapor phase epitaxial Mg doped GaN

A transmission electron microscopy study of structural defects induced by the introduction of Mg during the growth of metalorganic vapor phase epitaxy GaN is presented. These defects are assumed to be pyramidal inversion domains with an hexagonal base and ${112̄3}$ inclined facets. The tip of the pyramids is always pointing toward the $[0001̄]$ direction, i.e., in a Ga-terminated film, toward the substrate and in a N-terminated film, toward the surface. A chemical quantitative analysis shows that these pyramidal defects are Mg rich. They are present in all the studied films, independent of the doping level.