Epitaxial growth of ZrO2 on GaN templates by oxide molecular beam epitaxy

Molecular beam epitaxial growth of ZrO2 has been achieved on GaN (0001)/c-Al2O3 substrates employing a reactive H2O2 oxygen source. A low temperature buffer followed by in situ annealing and high temperature growth has been employed to attain monoclinic, (100)- oriented ZrO2 thin films. The typical full width at half maximum of a 30- nm- thick ZrO2 (100) film rocking curves is 0.4 arc deg and the root- mean- square surface roughness is similar to 4 angstrom. omega- 2 phi and pole figure x- ray diffraction patterns confirm the monoclinic structure of ZrO2. Data support an in- plane epitaxial relationship of ZrO2 [010] parallel to GaN [112(-)] and ZrO2 [001] parallel to GaN [11(-) 00]. X- ray diffraction and reflection high- energy electron diffraction analyses reveal in- plane compressive strain, which is mainly due to the lattice mismatch. (C) 2007 American Institute of Physics.