Epitaxial growth of ZrO_2 on GaN templates by oxide molecular beam epitaxy

摘要

Molecular beam epitaxial growth of ZrO_2 has been achieved on GaN (0001)/c-Al_2O_3 substrates employing a reactive H_2O_2 oxygen source. A low temperature buffer followed by in situ annealing and high temperature growth has been employed to attain monoclinic, (100)-oriented ZrO_2 thin films. The typical full width at half maximum of a 30-nm-thick ZrO_2 (100) film rocking curves is 0.4 arc deg and the root-mean-square surface roughness is ～4 A. ω-2θ and pole figure x-ray diffraction patterns confirm the monoclinic structure of ZrO_2. Data support an in-plane epitaxial relationship of ZrO_2 [010]‖GaN[112] and ZrO_2 [001]‖GaN[1100]. X-ray diffraction and reflection high-energy electron diffraction analyses reveal in-plane compressive strain, which is mainly due to the lattice mismatch.