Evidences of defect contribution in magnetically ordered Sm-implanted GaN

• We implanted Sm ions into wurtzite GaN thin films without secondary phase formation.
• Implantation-induced defects were identified by Raman-scattering and optical characterizations.
• Ferromagnetism and colossal moment were observed.
• Implantation-induced Ga vacancy is the possible medium for long-range magnetic order.

Samarium (Sm) ions of 200 keV in energy were implanted into highly-resistive molecular-beam-epitaxy grown GaN thin films with a focused-ion-beam implanter at room temperature. The implantation doses range between 1014 and 1016 cm−2. X-ray diffraction revealed Sm incorporation into GaN matrix without secondary phase. Raman-scattering spectroscopy identified impurity-independent defect-related oscillation modes. Slight decrease in band gap and significant reduction in transmittance were observed by optical transmission spectroscopy. Photoluminescence spectra showed emission peaks related to background p-type impurity. Ferromagnetic hysteresis loops were recorded from GaN implanted with highest Sm dose, and magnetic ordering was observed from Sm-implanted GaN with dose of and above 1015 cm−2. The long-range magnetic ordering can be attributed to interaction of Sm ions through the implantation-induced Ga vacancy.