Origin of split peaks in the oscillatory magnetoresistance in Al _xGa_1-x/NGaN heterostructures

The oscillatory magnetoresistance of the two-dimensional electron gas (2DEG) in Alx Ga1-x NGaN heterostructures has been studied by means of magnetotransport measurements at low temperatures and high magnetic fields. The split peaks of the Shubnikov-de Haas oscillations are observed at high magnetic fields, which are attributed to the spin splitting of the 2DEG. It is found that the spin splitting energy becomes smaller with an increase in magnetic field, indicating that the Zeeman spin splitting is not dominant at measured magnetic field range. Within this magnetic field range, the zero-field spin splitting, as well as Zeeman spin splitting, affects the split peaks in the oscillatory magnetoresistance of the 2DEG in Alx Ga1-x NGaN heterostructures.