Hydride vapor phase epitaxy growth of GaN on sapphire with ZnO buffer layers

The initial stages and subsequent growth of GaN on sapphire using ZnO buffer layers is reported for the hydride vapor phase epitaxy technique. A high gas-phase supersaturation in the growth ambient was used to favor a rapid initial growth on the substrate. A subsequent growth step was employed under conditions that favor a high lateral growth rate in order to promote the coalescence of the initial islands and provide optimal material properties. The specific gas-phase mole fractions of the GaCl and NH3 at the growth front control both the vertical and lateral growth rates. The use of a two-step growth process in the GaN growth leads to a controlled morphology and improved material properties for GaN materials when grown with a ZnO buffer layer. An optimized set of growth conditions, utilizing this two-step process, was found to also improve the growth directly on sapphire without a ZnO buffer layer.