Crystallinity evaluation of an uncoalesced broad wing region of GaN grown by epitaxial lateral overgrowth

Abstract The crystallinity of a gallium nitride (GaN) layer with a wide, uncoalesced wing region grown by epitaxial lateral overgrowth (ELO) was evaluated using X-ray diffraction, Raman spectroscopy, and cathodoluminescence (CL). The wing region, suspended above the mask, exhibited a small wing tilt of 81 arcsec, effectively mitigating strain-induced defects. After correcting for substrate curvature, the full width at half maximum (FWHM) of the GaN 0002 rocking curve was 63 arcsec. Raman spectroscopy of the E₂(high) mode showed a narrow FWHM of 1.9 cm −1 , indicating high crystallinity. CL imaging revealed a threading dislocation density of 2.5 × 10 5 cm −2 in the wing region, which is lower than that of commercially available free-standing GaN substrate. These results demonstrate that the ELO-GaN wing region achieves crystallinity comparable to or better than the free-standing GaN substrate, making it a promising candidate for micro-light-emitting diodes and short-cavity laser diode applications.