Nucleation and coalescence behavior for epitaxial ZnO layers on ZnO/sapphire templates grown by halide vapor phase epitaxy

The effects of growth conditions for ZnO layers grown by halide vapor phase epitaxy (HVPE) on (0 0 0 1) ZnO/sapphire templates are investigated. Micron-sized pyramidal ZnO islands nucleate on the template at the initial growth stage and each island grows differently with the process conditions. The high temperature of 1000 °C promotes a lateral growth rate and coalescence between the islands. The full-width at half-maximums (FWHMs) of X-ray rocking curves for the (0 0 0 2) and (1 0 1¯ 1) planes from a fully coalesced ZnO layer are quite narrow values below 160 arcsec. Transmission electron microscopy (TEM) reveals that screw character dislocations in the template do not propagate into the HVPE-grown layer.