Transport and spin properties of the two-dimensional electron gas in GaN-based heterostructures

Magnetotransport study has been performed on Al_xGa_1-xN/GaN heterostructures at low temperatures and high magnetic fields. The magneto-intersubband scattering effect of the two-dimensional electron gas (2DEG) has been observed in the triangular quantum well at the heterointerface. It is found that the effective mass of the 2DEG have strong dependence on the magnetic field and the 2DEG density due to the conduction band nonparabolicity in GaN. The zero-field spin splitting of the 2DEG in Al_xGa_1-xN/GaN heterostructures has been studied. The obtained zero-field spin splitting energy is 2.5 meV, and the obtained spin-obit coupling parameter is 2.2×10^-12 eVm. Meanwhile, the circular photo-galvanic effect induced by the spin-orbit interactions of the 2DEG in Al_xGa_1-xN/GaN heterostructures has also been investigated. The ratio of bulk inversion asymmetry and structure inversion asymmetry (SIA) terms is estimated to be about 13.2, indicating that the SIA is the dominant mechanism to induce the k-linear spin splitting of the subbands in the triangular quantum well at Al_xGa_1-xN/GaN heterointerfaces.