Recently, efficient spin injection, being the first step towards semiconductor spin electronics, could be accomplished by using BeMnZnSe as a spin filter. Such a spin filter made it possible to align the spin orientation of the conduction electrons and subsequently inject them into GaAs. However, controlling the spin orientation of conduction electrons by an external voltage would be very desirable. We therefore developed spin switch structures based on resonant tunneling through magnetic quantum wells with two separate spin-up and spin-down resonances, based on BeTe-ZnMnSe-BeTe. The tunneling carriers have subsequently been injected into a nonmagnetic GaAs p-i-n light emitting diode. The circular polarization of the emitted light is an indicator of the spin polarization of the injected electrons. At constant magnetic field and current, the degree of spin polarization could be changed from 81% to 38% by only varying the voltage across the magnetic resonant tunneling device.
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