Designing sapphire surface patterns to promote AlGaN overgrowth in hydride vapor phase epitaxy

Lateral overgrowth of patterned c-plane oriented sapphire substrates (PSS) with AlGaN using hydride vapor phase epitaxy was investigated with focus on how to suppress parasitic non c-planar crystallite nucleation and propagation. To this end, trigonal PSS was fabricated with either sidewalls parallel to sapphire {1-100}-facets or parallel to sapphire {-1100}-facets, which are crystallographically different due to the 3-fold sapphire symmetry. X-ray diffraction-based texture analysis and SEM were applied to find two types of (0001)_AlGaN ∥ (112 0)_sapphire -domains solely nucleating on PSS sidewalls close to {-1100}-facets. Their occurrence effectively blocks other orientations of non c-plane AlGaN crystallites allowing for quicker coalescence of c-plane AlGaN and improving overall AlGaN material quality.