High-temperature (HT) deposited buffer layer and flow modulation growth arc applied as two modulated techniques to the growth of high-quality GaN films by hydride vapor phase epitaxy. The characterization results, indicate that the use of HT buffer layer has improved the morphological. structural and optical properties of the GaN films. The improvement is due to the HT buffer layer that supplies both high-density nucleation centers and promotes the lateral growth of epitaxial film with a columnar structure, Moreover. the buffer layer is also helpful to relax the strain in the film. With the flow, modulation growth. the dislocation density in the films are greatly reduced and the homogeneity is highly improved. We attribute this promotion to the relaxation of strain and suppression of defects in sublayers and reconstruction of the as-grown surface of sublayers due to the interruption of the growth for a certain time. (C) 2002 Elsevier Science B,V. All rights reserved.