Effects of high-temperature annealing on magnetic properties of V-doped GaN thin films grown by MOCVD

Metal organic chemical vapor deposition (MOCVD) has been used to grow vanadium-doped GaN (GaN:V) on c-sapphire substrate using VCl4 as the V source. The as-grown GaN:V exhibited a saturated magnetic moment (Ms) of 0.28 emu/cm3 at room temperature. Upon high-temperature annealing treatment at 1100 °C for 7 min under N2 ambient, the Ms of the GaN:V increased by 39.28% to 0.39 emu/cm3. We found that rapid thermal annealing leads to a remarkable increase in surface roughness of the V-doped GaN as well as the electron concentration. The annealing also leads to a significant increase in the Curie temperature (TC), we have identified Curie temperatures about 350 K concluded from the difference between the field-cooled and zero-field-cooled magnetizations. Structure characterization by x-ray diffraction indicated that the ferromagnetic properties are not a result of secondary magnetic phases.