Defect reduction in HVPE growth of GaN and related optical spectra

GaN technology is still based on highly mismatched heteroepitaxial growth o n foreign substrates, and therefore needs to overcome a high defect density and a high level of stress in the epitaxial layers. Various attempts have been made to reduce the defects and stress in thick GaN layers. We here rep ort a reduction of the defect density in thick GaN layers grown by hydride vapour phase epitaxy, using regrowth on free-standing GaN films, as well as introducing an AlN buffer and AlN interlayer in the growth sequence. Speci al focus is put on the optical properties of the material.