A detailed transmission electron microscopy study of pyramidal defects appearing in highly Mg-doped GaN was reported. It was shown that these defects were closed pyramidal inversion domains. On the basis of a high-resolution microscopy study, atomic models were proposed for inversion domain boundaries which consist of Mg3N2 building blocks for both the basal and inclined facets of the pyramids. In Mg-doped GaN grown by metalorganic vapor phase epitaxy, these pyramidal inversion domains were a few nanometers wide, and their density was high enough to play a role in the free hole density decrease at high Mg doping.

Atomic Structure of Pyramidal Defects in Mg-Doped GaN. P.Vennéguès, M.Leroux, S.Dalmasso, M.Benaissa, P.De Mierry, P.Lorenzini, B.Damilano, B.Beaumont, J.Massies, P.Gibart: Physical Review B, 2003, 68[23], 235214 (8pp)