Spin splitting of conduction energies in GaAs-Ga0.7Al0.3As heterojunctions at B=0 and B≠0 due to inversion asymmetry

Anisotropic spin splitting of the conduction energy in GaAs-${\mathrm{Ga}}_{0.7}$ ${\mathrm{Al}}_{0.3}$As heterojunctions at B=0 is calculated, taking into account bulk and structure inversion asymmetry of the system. It is shown that both asymmetries are of importance. The theory accounts well for the recent Raman data. The effect of an external magnetic field on the spin splitting is also calculated. It is predicted that the splitting does not change sign as a function of the field.