  A longitudinal electric field is used to control the transit time (through an
undoped silicon vertical channel) of spin-polarized electrons precessing in a
perpendicular magnetic field. Since an applied voltage determines the final
spin direction at the spin detector and hence the output collector current,
this comprises a spin field-effect transistor. An improved hot-electron spin
injector providing ~115% magnetocurrent, corresponding to at least ~38%
electron current spin polarization after transport through 10 microns undoped
single-crystal silicon, is used for maximum current modulation.
