Microstructural Characterization of Semipolar GaN Templates and Epitaxial-Lateral-Overgrown Films Deposited on M-Plane Sapphire by Metalorganic Vapor Phase Epitaxy

Abstract

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∥[1100]GaN in-plane with a growth plane close to (1122)GaN. The microstructure of the templates is dominated by the presence of basal stacking faults with a density of around 3×105 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 5×103 cm-1. In these overgrown materials, the density of perfect dislocations is 108 cm-2 while neither partial dislocation nor prismatic stacking faults are observed.