Probing spin-polarized tunneling at high bias and temperature with a magnetic tunnel transistor

The magnetic tunnel transistor (MTT) is a three terminal hybrid device that consists of a tunnel emitter, a ferromagnetic (FM) base, and a semiconductor collector. In the MTT with a FM emitter and a single FM base, spin-polarized hot electrons are injected into the base by tunneling. After spin-dependent transmission through the ferromagnetic base they are collected in the conduction band of the semiconductor provided they have the right energy and momentum to overcome the Schottky barrier. Two factors determine the spin-sensitivity of the device: (i) spin-dependent tunneling from the emitter, and (ii) spin-dependent scattering of the hot electrons in the base. Since the magnetocurrent (MC) depends on the tunneling spin polarization, the MTT can be used to study the spin-polarization of ferromagnetic/insulator interfaces at high bias voltage. Moreover, the temperature dependence can be studied using a newly introduced lithographically defined MTT that allows us to probe the tunnel spin-polarization up to room temperature, removing a limitation of the standard technique of tunneling into a superconductor.