Cu-doped GaN thin films were grown by plasma-assisted molecular beam epitaxy. With nitrogen plasma only, films phase segregated into GaN and Cu-rich alloys. In contrast, when nitrogen-hydrogen plasma was used, the films were single-phased Ga1−xCuxN, with x as high as 0.04. Contrary to earlier studies, however, these films were not ferromagnetic, but rather paramagnetic in nature. First-principles calculations indicated that although each substitutional CuGa exhibited a moment of 1μB/Cu, it could be suppressed by neighbouring intrinsic defects such as N split interstitials.

Role of Nitrogen Split Interstitial Defects in the Magnetic Properties of Cu-Doped GaN. Y.Liu, Z.Gai, M.Weinert, L.Li: Physical Review B, 2012, 85[7], 075207