Growth of freestanding GaN crystals on three-dimensional mesh porous substrates by HVPE

Abstract

Novel three-dimensional mesh porous gallium nitride (GaN) substrates were prepared by a two-step method combining electrochemical etching and molten alkali etching. The porous GaN substrate facilitated the successful growth of self-separated GaN crystals via hydride vapor phase epitaxy (HVPE), achieving a thickness of around 1.5 mm. The nucleation and growth process on a three-dimensional mesh porous substrate was demonstrated. High-resolution X-ray diffraction full width at half maximum (FWHM) highlighted the superior quality of the GaN crystals grown on porous substrates. Cathodoluminescence (CL) testing showed a significant reduction in the dislocation density, and transmission electron microscopy (TEM) cross-sectional analysis revealed that the porous structure can effectively impede dislocation propagation. Our work provides a new technological route for the growth of high-quality self-separated GaN crystals.