Ferromagnetic Fe-Doped GaN Nanowires Grown by Chemical Vapor Deposition

We report the first synthesis and characterization of Fe-doped GaN nanowires. The Fe-doped nanowires were grown by chemical vapor deposition process, using pretreated iron oxide as dopant precursors. The morphological and structural analysis showed that the obtained nanowires were triangular cross section and single crystalline wurtzite GaN structure. It was proved that the pretreatment could induce doping effectively and higher substrate temperature could produce higher dopant concentration. The highest concentration of Fe ions in GaN was 0.12% in our condition. Fe 2p core-level X-ray photoelectron spectroscopy (XPS) spectra showed that the charge state of Fe transformed from +3 to +2 with the increase of Fe concentration. Moreover, the change in the binding energy of Ga 3p in the XPS spectra could be attributed to position change of Fermi level governed by Fe concentration. In the photoluminescence (PL) spectra, the relative intensity of exciton luminescence increased with Fe concentration. The magnetic measurement revealed the Fe-doped GaN nanowires were ferromagnetic at room temperature. The XPS results provided the evidence for the charge state of Fe dopant, indicating the intrinsic nature of room-temperature ferromagnetism of Fe-doped GaN nanowires.