The spin-dependent tunneling phenomenon in symmetric and asymmetric semiconductor heterostructures at zero magnetic field is studied theoretically on the base of a single conduction band and spin-dependent boundary conditions approach. It is shown that the spin-orbit splitting in the dispersion relation for the electrons in A III B V semiconductor quantum-tunneling structures can provide a dependence of the tunneling transmission probability on the electron's spin polarization. The dependence is calculated and discussed for different kinds of tunnel heterostructures.

Spin-dependent tunneling in symmetric and asymmetric double-barrier semiconductor heterostructures is studied. The effective one-band Hamiltonian approximation and spin-dependent boundary conditions approach are used for a theoretical investigation of the influence of electron spin on the tunneling probability. It is shown that spin-orbit splitting in the dispersion relation for electrons in A III B V semiconductors can provide the dependence of the tunneling transmission probability on the electron-spin polarization without additional magnetic field. The dependence can be controlled by an external electric field, and may be significant for realistic models of double-barrier semiconductor heterostructures. ͓S0163-1829͑99͒02320-6͔

The spin-dependent tunneling phenomenon in symmetric and asymmetric resonant semiconductor heterostructures is employed in a theoretical study to investigate the output tunnel current polarization at zero magnetic field. A simple model of the resonant tunneling structures and a simple one-electron band approximation with spin-orbit interaction are used in this work. It is shown that asymmetry in the electron distribution at the electrode regions provides spin-polarized tunnel current. An approach to optimize this spin-dependent effect is explored theoretically. In asymmetric resonant tunneling structures, we estimate theoretically that the polarization can reach 40% with a moderate applied electric field.