Using first-principles theoretical calculations, it was found that Ga-vacancies (VGa)

strongly interact with the Mn ions in GaN and thereby significantly affect the

electronic and magnetic properties. When Ga-vacancies were present in the

neighbourhood of the Mn ions, a charge transfer occurred from the Mn d band to

the acceptor level of VGa. Due to the depopulation of the Mn d band, the Fermi

level was generally lowered, and ferromagnetic exchange interactions between the

Mn ions were weakened, reducing the Curie temperature.

The Electronic Structure of Ga-Vacancy in Mn-Doped GaN. J.Kang, K.J.Chang:

Physica Status Solidi C, 2008, 5[9], 3035-7