Homoepitaxial growth of (0 0 0 1)- and (0 0 0 1̄) -oriented ZnO thin films via metalorganic vapor-phase epitaxy and their characterization

Homoepitaxial ZnO films have been grown via metalorganic vapor-phase epitaxy on O- and Zn-terminated basal-plane-oriented ZnO substrates. Maps of on-axis X-ray rocking curves obtained over 2-in-diameter ZnO{0001} wafers, diced from boules produced by vapor phase transport, revealed well-defined areas that ranged from <50 to >1050arcsec FWHM, indicating the presence of tilted domains. This macrostructure was manifested in all the homoepitaxial ZnO films deposited on these wafers. The films grown on O-terminated ZnO surfaces were initially dense. However, they changed to a textured polycrystalline microstructure after ≈100nm and possessed a surface roughness of 7.3nm. By contrast, the films grown on the Zn-terminated surface under the same conditions were fully dense, without texture and appeared to be monocrystalline with a significantly improved surface roughness of 3.4nm. Cross-sectional transmission electron microscopy of the wafers revealed high densities of edge dislocations and stacking faults with associated Frank partial dislocations.