  We propose and analyze a four-terminal metal-semiconductor device that uses
hot-electron transport through thin ferromagnetic films to inject and detect a
charge-coupled spin current transported through the conduction band of an
arbitrary semiconductor. This provides the possibility of realizing a spin
field-effect-transistor in Si, using electrostatic transit-time control in a
perpendicular magnetic field, rather than Rashba effect with spin-orbit
interaction.
