Control of crystallographic tilt in GaN grown on Si (111) by cantilever epitaxy

We have eliminated the crystallographic tilt associated with lateral growth during cantilever epitaxy by adjusting the lateral to vertical growth rate during the initial stages of growth. Cantilever epitaxy is a single growth run technique utilizing periodic, parallel mesas formed by etching the substrate. We have studied the relationship between the geometry of the “wing” region, the GaN spanning the etched trench, and the magnitude of crystallographic wing tilt. Cross-sectional scanning electron microscopy was used to characterize the geometry of the wing region, and x-ray diffraction was used to measure the magnitude of crystallographic tilt. It was found that by starting the GaN overgrowth with a slow lateral growth rate, compared to the vertical growth rate, a low tilt (⩽0.2°) was established and stabilized. The lateral growth rate can be increased during later stages of growth to assist in fast coalescence of neighboring stripes without significantly affecting the magnitude of crystallographic tilt.