Single-crystal GaN/Gd2O3/GaN heterostructure

Heteroepitaxy of single-crystal Gd2O3 on GaN (with a wurtzite hexagonal close-packed (hcp) structure) and single-crystal GaN on Gd2O3 was achieved. In situ reflection high-energy electron diffraction reveals a sixfold symmetry in the in-plane epitaxy of the rare earth oxide on GaN and also in the overgrowth of GaN on the oxide. 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 the lattice constant, the fully relaxed oxide films are of excellent structural quality. The x-ray diffraction results revealed that the GaN grown on the rare earth oxide is a single-crystal and has the same crystallographic hcp structure as the underlying GaN. The structures of both layers of GaN were also studied by cross section transmission electron microscopy. (C) 2002 American, Vacuum Society.