The early stages of hydride vapor phase epitaxy (HVPE) of GaN on sapphire were studied using atomic force microscopy, field-emission scanning electron microscopy, cross-sectional transmission electron microscopy, and x-ray diffraction rocking curves. At the high growth rate used (∼33 nm/s), the films appear to be fully coalesced for growth periods as short as 1 s. A distinct surface and subsequent bulk transformation were observed, resulting in significantly smoother film surfaces and improved bulk morphology. The growth of thick (i.e., 300 μm) GaN films using HVPE offers a promising technique for the deposition of high-quality substrates for GaN homoepitaxy.

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