Transmission electron microscopic evidence of spontaneous ordering in Mg-doped bulk crystals, grown using a high-pressure high-temperature process, was reported for the first time. The ordering consisted of Mg-rich planar defects which formed on basal planes that were separated by 10nm, and occurred only for growth with (00•¯1)N polarity. The ordering led to the formation of satellite diffraction spots which divided the (00•1) reciprocal lattice distance into 20 parts. This so-called micro-superlattice could be described as polytypoids, comprising planar defects with some of the characteristics of inversion domain boundaries.

Spontaneous Ordering in Bulk GaN:Mg Samples. Z.Liliental-Weber, M.Benamara, J.Washburn, I.Grzegory, S.Porowski: Physical Review Letters, 1999, 83[12], 2370-3