Interface Contributions to the Spin-Orbit Interaction Parameters of Electrons at the (001) GaAs/AlGaAs Interface

One-body mechanisms of spin splitting of the energy spectrum of 2D electrons in a one-side doped (001) GaAs/Al$_x$Ga$_{1-x}$As quantum well have been studied theoretically and experimentally. The interfacial spin splitting has been shown to compensate (enhance) considerably the contribution of the bulk Dresselhaus (Bychkov-Rashba) mechanism. The theoretical approach is based on the solution of the effective mass equation in a quasitriangular well supplemented by a new boundary condition at a high and atomically sharp heterobarrier. The model takes into account the spin-orbit interaction of electrons with both bulk and interfacial crystal potential having C$_{2v}$ symmetry, as well as the lack of inversion symmetry and nonparabolicity of the conduction band in GaAs. The effective 2D spin Hamiltonian including both bulk and interfacial contributions to the Dresselhaus ($\alpha_{BIA}$) and Rashba ($\alpha_{SIA}$) constants has been derived. The analytical relation between these constants and the components of the anisotropic nonlinear $g$-factor tensor in an oblique quantizing magnetic field has been found. The experimental approach is based, on one hand, on the detection of electron spin resonance in the microwave range and, on the other hand, on photoluminescence measurements of the nonparabolicity parameter. The interfacial contributions to $\alpha_{BIA}$ and $\alpha_{SIA}$ have been found from comparison with the theory.