Dependence of magnetic properties on the growth conditions of MnGaN grown by rf N plasma molecular beam epitaxy

MnGaN has been grown by radio frequency N plasma-assisted molecular beam epitaxy. MnGaN samples were grown on MOCVD GaN(0001)/sapphire(0001) at substrate temperature of 550°C under different Ga/N flux ratios leading to 4 different growth regimes: N-rich, slight metal-rich, metal-rich, and Ga-rich. It is found that in the case of MnGaN, Mn incorporation and hence magnetic properties clearly depend on the growth conditions. Briefly, it is found that the N-rich conditions give a sample with much larger magnetization compared to the other samples. Slight metal-rich and metal-rich grown samples have very little magnetization. Finally, Ga-rich grown samples have intermediate level of magnetization. Possible origins of the magnetization are discussed. Ga-rich magnetization is attributed to accumulates, but N-rich magnetization is attributed to carrier-mediated ferromagnetism and/or ferromagnetism due to clusters.