Pyramidal defect formation in view of magnesium segregation

Abstract

The formation process of pyramidal defects in Mg doped GaN grown by metal organic vapor phase epitaxy (MOVPE) was studied by means of transmission electron microscopy (TEM). The formation process is ascribed to the segregation of Mg on the surface during growth. A segregation model explains the onset of defect formation. The model yields a low incorporation coefficient of only 1% per grown bilayer from surface states into the bulk material. The observed modulation of the defect density is explained by an efficient reduction of Mg on the surface by the formation of the pyramidal defects. Layers optimized on the basis of this model are demonstrated to be free of pyramidal defects.