By means of first-principles calculations, an investigation was made of the effects of various Li-doping on the exchange interaction and the formation energy in bulk GaN with Ga vacancies. Although the Ga vacancies could induce ferromagnetism in GaN, their formation energy was rather high. The calculations showed that Li-doping could effectively tune the formation energy of Ga vacancies. It was revealed that the stabilizing effect depended on whether the number of holes was increased or decreased after Li-doping. When Li atoms substitutes for N atoms or occupies the interstitial sites, the holes were reduced and the formation energy of Ga vacancies was lowered. In contrast, Li substituting for Ga generates additional holes in the system, leading to an enhancement of the formation energy of Ga vacancies and making the system less stable.

Stabilizing the Defect-Induced Dilute Magnetic Semiconductors: Li-Doping in GaN with Ga Vacancies. J.Nisar, X.Peng, T.W.Kang, R.Ahuja: EPL, 2011, 93[5], 57006