  A theory of spin-dependent electron transmission through resonant tunneling
diode (RTD) grown of non-centrosymmetrical semiconductor compounds has been
presented. It has been shown that RTD can be employed for injection and
detection of spin-polarized carriers: (i) electric current flow in the
interface plane leads to spin polarization of the transmitted carriers, (ii)
transmission of the spin-polarized carriers through the RTD is accompanied by
generation of an in-plane electric current. The microscopic origin of the
effects is the spin-orbit coupling-induced splitting of the resonant level.
