  A large spin-dependent and electric field-tunable magnetoresistance of a
two-dimensional electron system (2DES) is a key ingredient for the realization
of many novel concepts for spin-based electronic devices. The low
magnetoresistance observed during the last decades in devices with lateral
semiconducting (SC) transport channels between ferromagnetic (FM) source (S)
and drain (D) contacts has been the main obstacle for realizing spin field
effect transistor proposals. Here, we show both, a large two terminal
magnetoresistance in lateral 2DES-based spin valve geometry, with up to 80%
resistance change, and tunability of the magnetoresistance by an electric gate.
The large magnetoresistance is due to finite electric field effects at the
FM/SC interface, which boost spin-to-charge conversion. The gating scheme we
use is based on switching between uni- and bi-directional spin diffusion,
without resorting to the spin-orbit coupling.
