Inversion domain boundary structure of laterally overgrown c-GaN domains including the inversion from Ga to N polarity at a mask pattern boundary

During epitaxial lateral overgrowth, the lateral polarity inversion of c-GaN domains from Ga to N polarity, triggered at the boundary of an SiO2 mask pattern, resulted in inversion domain boundaries (IDBs) forming preferentially on the \{11{\overline 2}0\} plane, although the formation energy of IDBs on the \{1{\overline 1}00\} plane is known to be lower than that on the \{11{\overline 2}0\} plane. A model that takes a geometrical factor into consideration can explain this preferential tendency of IDB formation on the \{11{\overline 2}0\} plane, and computational simulations based on the proposed model are consistent with experimental results. In contrast with the vertically upright IDBs observed in N-to-Ga polarity inversion, vertically slanted IDBs were formed in some samples during the inversion from Ga to N polarity. These polarity inversions, which appeared to randomly occur on the mask pattern, turned out to be triggered at the mask pattern boundaries.