Improvements in (112̅2) semipolar GaN crystal quality by graded superlattices

We report on the use of graded superlattices (SLs) for defect reduction in semipolar (112̅2) GaN films, grown by metal-organic chemical vapor deposition. High-resolution x-ray diffraction analysis revealed that there was a great reduction in the full width at half maximum, both on-axis and off-axis, with the SLs. Atomic force microscopy images revealed a significant decrease in slate features which was associated with the basal-plane stacking faults. The transmission electron microscopy images showed that the threading dislocation was greatly reduced after the graded superlattices. Room temperature photoluminescence measurement revealed that the band-edge emission intensity increased with the insertion of the SLs, which suggested reduction in the nonradiative recombination centers.