Microstructural characterization of semipolar GaN templates and epitaxial-lateral-overgrown films deposited on M-plane sapphire by metalorganic vapor phase epitaxy

The microstructure of GaN templates and epitaxial lateral overgrown (ELO) films deposited on M-plane sapphire is investigated by transmission electron microscopy. The epitaxial relationship is [1120](sapphire) parallel to [1100](GaN) in-plane with a rmvth plane close to (1122)(GaN). The microstructure of the templates is dominated by the presence of basal stacking faults with a density of around 3 x 105 cm(-1). Basal stacking faults are either terminated by partial dislocations or connected by prismatic stacking faults. Perfect dislocations are also observed. ELO films with stripes parallel to [1100](GaN) allow us to reduce the density of basal stacking faults in the overgrown regions down to 5 x 10(3) cm(-1). In these overgrown materials, the density of perfect dislocations is 10(8) cm(-2) while neither partial dislocation nor prismatic stacking faults are observed.