Effect of Carrier Gas on Crystal Quality of Thick HVPE-GaN Films

The effect of carrier gas on thick GaN film grown by hydride vapor phase epitaxy on (0001) sapphire substrate has been studied by double crystal X-ray diffraction (DCXRD), polarizing microscope and field emission scanning electron microscope (FE-SEM). H₂, as carrier, is propitious to two-dimension growth pattern of GaN film but causes production of more defects and impurities. N₂, as carrier, weakens pre-reaction and reduces content of defects and impurities, however, growth interface of GaN forms easily crystallographic facets but not epitaxial (0002) plane, which leads to appearing of protuberances. It may gain high crystal quality that first H₂ and then N₂ is adopted as carrier gas.