Abstract: Changes in the GaN growth surface morphology and material quality by the addition of H₂ into the N₂ carrier gas during HVPE are reported. Hydrogen in the growth ambient leads to materials with a narrow bandedge emission photoluminescence （PL） and a decreased linewidth of （0002） symmetric and （1014） asymmetric X ray diffraction rocking curves. The change of the GaN growth by H₂ addition has been ascribed to a reduction in the NH₃ gas phase reactions in the presence of H₂, leading to a lower N activity at the surface. The lower N activity would then lead to an enhanced surface diffusion of Ga adatoms and these subsequently changes in material properties and structures.