Exchange Enhancement of Spin-Splitting in Al_xGa_1−xN/GaN Heterostructures in Tilted Magnetic Fields

Al_xGa_1−xN/GaN heterostructures are investigated by magnetotransport experiments in tilted magnetic fields at low temperatures. The spin-split peaks of the Shubnikov-de Haas (SdH) oscillations are observed at high magnetic fields, which are attributed to the Zeeman spin-splitting of the two-dimensional electron gas at the heterointerface. The exchange enhanced g^* of the spin-splitting is investigated by measuring the positions of the pairs of spin-split SdH maxima. Moreover, it is found that g^* becomes smaller with the increasing tilt angle, which suggests the anisotropy of g^* is due to the strong polarization-induced electric field at the Al_xGa_1−xN/GaN heterointerface.