Carrier-mediated ferromagnetism in InGaGdN grown by plasma-assisted molecular beam epitaxy

InGaGdN layers and InGaGdN/GaN and InGaN/GaGdN superlattice (SL) structures were grown on (0001) sapphire substrates or MOVPE-grown GaN templates by plasma-assisted molecular beam epitaxy. Si co-doping into InGaGdN and GaN barrier layers of SL structures were also conducted. Non-existence of secondary phase and the Gd atom substitution of Ga sites were confirmed by X-ray diffraction and X-ray absorption fine structure measurements. Luminescence properties of InGaGdN were also observed at room temperature with the emission peak energy red-shifts corresponding to the InN molar fraction. Clear hysteresis and saturation were observed in the magnetization versus magnetic field (M-H) curves measured at room temperature for the InGaGdN single-layers and InGaGdN/GaN SLs. The magnetic properties of the Gd-doped InGaN are understood to be closely related to the carrier-mediated magnetism.