Structural study of GaN grown on nonpolar bulk GaN substrates with trench patterns

The selective-area growth of GaN (SAG-GaN) films on nonpolar bulk GaN substrates with trench patterns was performed by metalorganic vapor phase epitaxy. We investigated the transformation of SAG-GaN facet structures by changing the direction of the trench patterns. Anisotropic SAG-GaN structures with the () facet on the (0001) plane sidewall, the () facet on the top surface, and the () facet on the () plane sidewall appeared for trench patterns along the a-axis. The width of () facets decreased whereas () facets expanded with increasing off angle of trench patterns from the a-axis. On the other hand, hexagonal facet structures with {} facets appeared for trench patterns along the c-axis. () facets on the top surface expanded with increasing off angle of trench patterns from the c-axis, similar to the results of using trench patterns along the a-axis. Basal-plane stacking faults were annihilated by using trench-patterned substrates. Low basal-plane stacking fault (BSF) density and faster coalescence were obtained for the off angle of trench patterns of around 6° from the c-axis.