Effective mass of the two-dimensional electron gas and band nonparabolicity in Al_xGa_1-xN/GaN heterostructures

Magnetotransport study has been performed on Alx Ga1-x NGaN heterostructures at low temperatures and high magnetic fields. Effective-mass values of the two-dimensional electron gas (2DEG) in the triangular quantum well at the heterointerfaces are obtained by analyzing the temperature-dependent Shubnikov-de Haas oscillations. It is found that the values have strong dependence on the magnetic field and the 2DEG density. Our results show that the effective mass increases 0.01 m0 T and 0.0027 m0 electron density of 1012 cm-2. Such behavior is thought to be due to the conduction band nonparabolicity in GaN. The extrapolated band edge effective mass of m0* = (0.145±0.006) m0 is obtained, which is smaller than most reports that neglected the influence of the magnetic field in Alx Ga1-x NGaN heterostructures.