Single crystal rare earth oxides epitaxially grown on GaN

New single crystals of Gd/sub 2/O/sub 3/ and Y/sub 2/O/sub 3/ were found to grow epitaxially on GaN in ultra-high vacuum. In-situ reflection high-energy electron diffraction reveals a six-fold symmetry in the in-plane epitaxy of the rare earth oxides. Single-crystal X-ray diffraction measurements find that these single-crystal oxide films are indeed the high temperature hexagonal phases of the sesquioxides, stabilized by the GaN substrate epitaxy. Despite a large mismatch in lattice constant the fully relaxed oxide films are of excellent structural quality.