Reactor and growth process optimization for growth of thick GaN layers on sapphire substrates by HVPE

In total, 120 μm thick GaN layers without cracks have been grown on 2 in sapphire substrates by hydride vapor phase epitaxy. This has been achieved by optimization of the flow patterns in the reactor based on 3D process modelling, choice of the growth parameters especially the carrier gas composition and the usage of suitable GaN/sapphire templates. An important finding is that an H2 content of around 50% in the N2 carrier yields the lowest crack density.