Electron-spin polarization by resonant tunneling

The spin-dependent electron resonant tunneling through nonmagnetic III–V semiconductor asymmetric double barriers is studied theoretically within the envelope function approximation and the Kane model for the bulk. It is shown, in particular, that an unpolarized beam of conducting electrons can be strongly polarized, at zero magnetic field, by a spin-dependent resonant tunneling, due to the Rashba mesoscopic spin-orbit interaction. The electron transmission probability is calculated as a function of the electron’s energy and angle of incidence. Specific results for tunneling across lattice matched politype ${\mathrm{Ga}}_{0.47}{\mathrm{In}}_{0.53}\mathrm{As}$/InP/${\mathrm{Ga}}_{0.47}{\mathrm{In}}_{0.53}\mathrm{As}$/${\mathrm{GaAs}}_{0.5}{\mathrm{Sb}}_{0.5}$/${\mathrm{Ga}}_{0.47}{\mathrm{In}}_{0.53}\mathrm{As}$ double barrier nanostructures show, for instance, sharp spin-split resonances, corresponding to resonant tunneling through spin-orbit split quasibound ground and excited electron states (quasisubbands). The calculated polarization of the transmitted beam in resonance with the second quasisubband shows that polarization bigger than 50% can be achieved with this effect.