Thick GaN Epitaxial Growth with Low Dislocation Density by Hydride Vapor Phase Epitaxy

Thick GaN layers were grown by hydride vapor phase epitaxy (HVPE) with the aim of using these layers as a homoepitaxial substrate to improve device quality of laser diodes or light emitting diodes. HVPE is very useful for thick layer growth since the growth rate can reach from several ten up to one hundred micron per hour. In this experiment, the growth began as selective growth through openings formed in a SiO₂ mask. Facets consisting of {1101} planes were formed in the early stage and a continuous film developed from the coalescence of these facets on the SiO₂ mask. As a result, GaN layers with a dislocation density as low as 6×10⁷ cm^-2 were grown on 2-inch-diameter sapphire wafers. These GaN layers were crack-free and had mirror-like surface.