Ga-vacancy-induced room-temperature ferromagnetic and adjusted-band-gap behaviors in GaN nanoparticles

Abstract

Room-temperature ferromagnetism has been found in Ga-deficient GaN grown using the direct reaction of Ga 2 O 3 powder with NH 3 gas. The observed magnetism in GaN induced by Ga vacancies is investigated both experimentally and theoretically. First-principles calculations reveal that the spontaneous spin polarization is created by the 3.0 μ B local moment for GaN and magnetism originates from the polarization of the unpaired 2 p electrons of N surrounding the Ga vacancy. At the same time, the band gap can be also adjusted by changing the Ga-vacancy concentration.

Ga-vacancy induced room temperature ferromagnetism observed in N-irradiated GaN films

“…Nonetheless, the origin and mechanism of DIM in GaN-based DMSs also have not reached a unanimous opinion so far. For instance, some experimental researchers observe room temperature ferromagnetism (RTFM) in GaN nanoparticles or films and attribute it to Ga-related vacancies [13][14][15]. However, ferromagnetism cannot reach to room temperature when the vacancy density is lower than 10 21 cm −3 , which has been predicted by theoretical calculations [16].…”

Influence of Ga vacancies, Mn and O impurities on the ferromagnetic properties of GaN micro- and nanostructures

“…% (sample 3) causes V Ga point-defects that could participate in the generation of ferromagnetism, as other authors have suggested. Ren et al and Jeganathan et al 44,45 recently reported ferromagnetism in gallium-deficient GaN nanoparticles and nanowires, respectively, in which both groups vary the Ga flux during the synthesis of the nanostructures and correlate the gallium deficiency, detected by EDS or XPS, to the generation of V Ga . These measures were correlated with PL measurements that confirmed the presence of gallium vacancies due to its electronic transitions, similarly to the CL measurements present in this work, because the sensitivity of these techniques to detect the characteristic defect-related optical transition has been broadly demonstrated.…”

Free-Standing Self-Assemblies of Gallium Nitride Nanoparticles: A Review

“…More detailed experiments showed that the optical absorption edge moved to longer wavelengths (red-shifted) as the concentration of Ga vacancies increased [ 112 ]. Figure 3 shows the effect of Ga vacancy on UV-vis spectrum of GaN nanoparticles.…”

“…The band-gap of GaN nanoparticles increased with decreasing concentration of Ga vacancy. The band-gap of Ga N nanparticles with the concentration of Ga vacancy of 2.8% was , for Ga N nanoparticles with the concentration of Ga vacancy of 1.8%, and for Ga N nanoparticles with the concentration of Ga vacancy of 1.6% [ 112 ].…”

“…Furthermore, the saturation magnetic moment decreased with increasing nanoparticles size, suggesting that ferromagnetism was due to the surface defects of the nanoparticles. Recently experiments indicated the ferromagnetism should be induced by Ga vacancies [ 112 ].…”