Microstructural properties of over-doped GaN-based diluted magnetic semiconductors grown by MOCVD
MOCVD制备过掺杂GaN基稀磁半导体微结构研究

We have grown transition metal (Fe, Mn) doped GaN thin films on c-oriented sapphires by metal organic chemical vapor deposition (MOCVD). By varying flow of metal precursor, series of samples with different ion concentration are synthesized. Microstructural properties are characterized by high-resolution transmission electron microscope (HRTEM). For Fe over-doped GaN samples, hexagonal Fe3N clusters are observed with Fe3N(0002) parallel to GaN(0002) while for Mn over-doped GaN, hexagonal Mn6N2.58 phase are observed with Mn6N2.58(0002) parallel to GaN(0002). Meantime, with higher concentration ions doping into the lattice matrix, the partial lattice orientation is distorted, leading to the tilt of GaN (0002) planes. Magnetic measurement show that the homogeneous Fe doped GaN samples are ferromagnetic and Mn doped GaN are not ferromagnetic. The magnetization of Fe over-doped GaN sample promotes a lot which is ascribed to the participation of ferromagnetic iron and Fe3N while Mn over-doped sample show very weak ferromagnetic behavior which may probably originate from Mn6N2.58.