Structural and morphological characteristics of planar (112̄0) a-plane gallium nitride grown by hydride vapor phase epitaxy

Abstract

This letter discusses the structural and morphological characteristics of planar, nonpolar (112̄0) a-plane GaN films grown on (11̄02) r-plane sapphire by hydride vapor phase epitaxy. Specular films with thicknesses over 50 μm were grown, eliminating the severely faceted surfaces that have previously been observed for hydride vapor phase epitaxy-grown a-plane films. Internal cracks and crack healing, similar to that in c-plane GaN films, were observed. Atomic force microscopy revealed nanometer-scale pitting and steps on the film surfaces, with rms roughness of ∼2 nm. X-ray diffraction confirmed the films are solely a-plane oriented with on-axis (112̄0) and 30° off-axis (101̄0) rocking curve peak widths of 1040 and 3000 arcsec, respectively. Transmission electron microscopy revealed a typical basal plane stacking fault density of 4×105 cm−1. The dislocation content of the films consisted of predominately edge component (bedge=±[0001]) threading dislocations with a density of 2×1010 cm−2, and mixed-character Shockley partial dislocations (b=13〈11̄00〉) with a density of 7×109 cm−2.