Computational insights into optoelectronic and magnetic properties of V(III)-doped GaN

First-principles calculations have been carried out to investigate the optoelectronic and magnetic of Ga_1-xV_xN (x ​= ​0, 0.027, 0.0625 and 0.125). Our results demonstrate that V(III) doping at Ga site not only affect the magnetic state of the GaN, but also significantly modify the electronic structure by generating impurity-derived states. The ferromagnetic coupling between V(III) ions is due to super-exchange mechanism. The super-exchange ferromagnetic mechanism is confirmed from the analysis of electronic structure and the arrangement of V(III) ions in the lattice of GaN crystal. We have estimated the Curie temperature (Tc) for different concentrations (5.5%, 12.5% and 25%) of V(III) ions within the mean field approximation and found that Tc can be expected above room temperature at higher concentration (>12%) of V(III) ions. The optical properties have been investigated using optical absorption spectra and we found that the V(III) doping increases the fundamental bandgap of GaN. The observed spin allowed d-d transition (³A₂ to ³T₂ transition) bands of V(III) ions take place in the visible region of the absorption spectrum and shows a red-shift with increasing V(III) content. Furthermore, the correlation of magnetic interaction with d-d transition of V(III) ions and bandgap of GaN is also discussed and we found that d-d transition bands show a red/blue shift for FM/AFM coupled V(III) ions. It is also observed that the fundamental bandgap of GaN in AFM is higher than that in FM configuration.