Observation of crystallographic wing tilt in cantilever epitaxy of GaN on silicon carbide and silicon (111) substrates

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Abstract
We have characterized the growth of GaN on both SiC and Si (111) using the cantilever epitaxy technique. Cantilever epitaxy employs growth from periodic, parallel mesas which are formed by etching the substrate [C.I.H. Ashby et al. Appl. Phys. Lett. 77, 3233 (2000)]. GaN/AlN/Si and GaN/AlN/SiC layers were grown via metalorganic chemical vapor deposition on substrates with reactive ion etched trenches. This single step approach allows GaN to laterally overgrow the substrate trenches yielding low defect density material over the trench, while avoiding use of a mask which is commonly employed in lateral epitaxial overgrowth. Scanning electron microscopy, atomic force microscopy, and x-ray diffraction were used to characterize the resulting material. Significant threading dislocation reduction was observed in the “wing” regions (the material directly over the trenches). Contrary to previous reports, crystallographic wing tilt ranging from 0.22° to 0.77° was also observed, despite the absence of a wing/mask interface using this technique.