Structural and morphological characteristics of planar (11(2)over-bar0) a-plane gallium nitride grown by hydride vapor phase epitaxy
This letter discusses the structural and morphological characteristics of planar, nonpolar (11 (2) over bar0) a-plane GaN films grown on (1 (1) over bar 02) r-plane sapphire by hydride vapor phase epitaxy. Specular films with thicknesses over 50 mum 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 similar to2 nm. X-ray diffraction confirmed the films are solely a-plane oriented with on-axis (11 (2) over bar0) and 30degrees off-axis (10 (1) over bar0) rocking curve peak widths of 1040 and 3000 arcsec, respectively. Transmission electron microscopy revealed a typical basal plane stacking fault density of 4x10(5) cm(-1). The dislocation content of the films consisted of predominately edge component (b(edge)=+/-) threading dislocations with a density of 2x10(10) cm(-2), and mixed-character Shockley partial dislocations (b=1/3(1) over bar 00>) with a density of 7x10(9) cm(-2). (C) 2003 American Institute of Physics.