Influence of Dopants on Defect Formation in GaN

The influence of p-dopants (Mg and Be) on the structure of GaN has been studied using Transmission Electron Microscopy (TEM). Bulk GaN : Mg and GaN : Be crystals grown by a high pressure and high temperature process and GaN : Mg grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. A structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering in bulk GaN : Mg on 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 empty inside (pinholes) were observed. Both these defects were also observed in MOCVD grown crystals. Pyramidal defects were also observed in the bulk GaN : Be crystals.