Spontaneous Ordering in Bulk GaN:Mg Samples

Transmission electron microscopy evidence of spontaneous ordering in Mg-doped, bulk GaN crystals grown by a high pressure, high temperature process is reported for the first time. The ordering consists of Mg-rich planar defects formed on basal planes separated by 10 nm and occurs only for growth with $\left(000\overline{1}\right)$ N polarity. The ordering leads to the formation of satellite diffraction spots dividing the (0001) reciprocal lattice distance into 20 parts. This “microsuperlattice” can be described as polytypoids comprised of planar defects with some characteristics of inversion domain boundaries.