The influence of p-dopants (Mg, Be) upon the structure was studied by using transmission electron microscopy. Bulk GaN:Mg and GaN:Be crystals, grown using a high-pressure high-temperature process, and GaN:Mg grown using metal-organic chemical vapor deposition were studied. A structural dependence upon growth polarity was observed in bulk crystals. Spontaneous ordering in bulk GaN:Mg, on the c-plane (formation of Mg-rich planar defects with characteristics of inversion domains) was observed for growth in the N to Ga polar direction (N polarity). On the opposite side of the crystal (growth in the Ga to N polar direction), Mg-rich pyramidal defects which were empty within (pinholes) were observed. Both of these defects were also observed in metalorganic chemical vapor deposition grown crystals. Pyramidal defects were also observed in bulk GaN:Be crystals.

Influence of Dopants on Defect Formation in GaN. Z.Liliental-Weber, J.Jasinski, M.Benamara, I.Grzegory, S.Porowski, D.J.H.Lampert, C.J.Eiting, R.D.Dupuis: Physica Status Solidi B, 2001, 228[2], 345-52