Rashba spin splitting for the first two subbands in AlxGa1−xN/GaN heterostructures

By solving Schrödinger and Poisson equations self-consistently for AlxGa1−xN/GaN heterostructures grown along the cc axis, the spatial distribution of electrons and the energy of all the bound states confined in heterostructures are obtained, and electrons are found to occupy the first two subbands. Considerable magnitude of the Rashba spin splitting for the first two subbands at the Fermi level is obtained. Changes of the Rashba spin splitting with the Al composition in the barrier are calculated. The effect of electrons taking up more than one subband on the Rashba spin splitting for the first subband is discussed. Individual factors contributing to the Rashba spin splitting are discussed in detail, and the contribution to the Rashba coefficient from the well and the heterointerface are found to be much more than that from the barrier. The results show that a high density of the 2DEG and the internal electric field caused by the piezoelectric polarization and the spontaneous polarization are crucial for considerable Rashba spin splitting for AlxGa1−xN/GaN heterostructures.