Bulk GaN substrate with overall dislocation density on the order of 10^sup 5^/cm^sup 2^ fabricated by hydride vapor phase epitaxy

In this study, a combined facet and flattening (FF) growth technique was implemented to fabricate GaN substrates by hydride vapor phase epitaxy. By changing the growth conditions, i.e., the growth temperature and V/III ratio, it was found that facet growth was promoted with a high V/III ratio and low temperature and planar growth was promoted with low V/III ratios and high temperature. We introduce a FF growth technique involving further reduction of the dislocation density using facet growth as the first step and flattening growth of the GaN layer as the second step. To further reduce dislocation density, we also finally demonstrate a multiple-step growth technique based on FF growth and succeeded in producing GaN substrates with overall dislocation densities on the order of 105 cm-2.